Expiring Coins (thought experiment)

It’s just a thought experiment, but maybe somebody finds it interesting.

What if coins would expire after a time, if not used?

I understand there’s not necessarily a need for reclaiming “lost coins” (or so I heard), and having to use them just to keep them alive is sure an inconvenience (not as much as it first sounds, but more on that in a bit.) Anyway, here’s the idea.

Let’s say, a coin expires 4 (1, 2, 5, 10, 20, …?) years after it was last used. In effect, if somebody wants to pay with a coin that they received more than 4 years ago, it’s not going to be accepted.

When a coin is divided, the parts will expire after half the time the full coin would, if a half is divided then its part after a quarter of the time, and so on.

For additional magic, the expiry time could depend on something that is tied to a coin’s market value. For example, if the available supply is high, the expiry time goes down, but if it’s low, the time goes up. If set properly, large value denominations (full coins, half coins, …) would live long enough to be convenient for savings, while smaller denominations (16th coins, 32nd coins, …) would serve as change.

A hidden benefit of such a system would be that smaller denominations (as they are more inconvenient with the constant need to renew them) would tend to be exchanged into larger ones (or quietly return to the ground), so “dust” would not accumulate.


Doesn’t this result in people losing their money?


Yes, and I think this is the human element.

People are motivated to do something with the coin. Like spend it to upload, trade it, etc

The workaround with this scheme will be a simple APP that moves all ones coin from one address to another.

So it will nullify the scheme and no benefits of the scheme


I have heard the idea talked about before. I don’t like the social engineering aspect of the concept I read about. Essentially they wanted to promote the spending (the idea is great economies are created by spending) and fight against hording.

To me social engineering is a threat to freedom. I want the prospect of leaving my children’s children an inheritance. I do like the idea of whole denominations being forever and partials expiring perhaps. Especially if partials are hurting the network (if we were talking safe coin or something like it). I would also want a built in way to convert my partials to wholes and not have to trade partials for wholes on some kind of exchange. And eventually the whole might be worth too much to easily create, but you covered this with the idea of market value…

Plain and simple, I’m against social engineering and this has that smell about it, but I’m trying to be open minded.


It doesn’t, but it can. One of the ideas is that if something is not touched, it may be lost, so let’s recover it.

Or, to exchange it to bigger coins (assuming coins will be divisible, which is a necessary element of this idea) because bigger coins last longer.

People can have a savings account and a checking account; it’s about the same.

The primary benefit of the scheme is to encourage people (actually, wallet apps) to exchange smaller divisions into larger ones, because those are less hassle. I argue that is beneficial because: 1) less pieces of SD floating around, 2) divided coins can be put back together more likely.

To be honest, I have no idea how the halves will find each other, but that is outside the scope of this idea.


I think you misunderstood. You don’t need to spend a coin, you can just “touch” it (resend it to yourself.) More likely, you would just exchange two of your halves to a whole (or 2 16th to an 8th, etc) to get a coin that needs to be “renewed” less often. We’ll need a wallet app to deal with putting together what we wanna pay to somebody from the different divisions, and this too would be done behind the curtains; the users wouldn’t have to do anything.

Again: the primary goal is to reduce the amount of pieces floating around. An additional benefit is that lost coins would get magically reclaimed.


“Self Destruct buttons” are pretty common in cartoons, but rather silly in real life.

If a coin is never spent, it’s value flows back into the system anyway…

A lot of work, all to make things more complicated than they need to be. I see little benefit for a ton of complexity.


When I used to hear people argue that 21m BTC was too few, I considered the idea of something similar to BTC, but that had a 1% a year inflation rate. I figured doubling the amount over 100 years was so far superior to what we have with money today, that it wouldn’t compromise peoples’ wealth much, and we wouldn’t have to worry about the last of it getting lost somehow. I have long been of the opinion that there are lot fewer BTC available then people think, and that number will eventually stop growing, but some will inevitably be lost.

Then it occurred to me that it would be a bad thing if any CC made today would still be the height of CC tech in 20 years, and therefore it likely wouldn’t matter all that much.

Personally, if you’re going to have expiring coins, I’d have it be a minimum of around 150 years, so that they never expired in someone’s lifetime (which would likely need to be increased one day), so it would be of little benefit for what you’re talking about. It is appealing to have a limit to the size of a blockchain for the old school CC tech, just so it doesn’t grow perpetually.

I like the idea of a network being able to salvage lost credit, but I think having them be nearly infinitely divisible solves that issue well enough for me.

On an unrelated note; It’s funny… there are a handful of traits among the CCs out there that I like for different reasons, and whenever I start thinking that I’d kind of like to invest in one, I’m reminded of how far superior Safecoin will be, and I invest in some more Maidsafecoin.

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Let me focus again on this little piece: social engineering is evil.

However, it is very different from setting up rules that result in a behavior that benefits the system. Which is good.

Extreme example: “If you drive very fast, you pay a lot of money.” Most people don’t like to pay (or lose their license), so they don’t speed (too much), and that results in fewer traffic accidents. Laws are “social engineering” in a way: they alter behavior, but it’s for the benefit of everybody. (Disclaimer: I’m aware that many laws are not for the benefit of everybody; I’m just illustrating a concept :smirk_cat:)

A rule that goes against the mindless divisions of coins seem to be beneficial.

And honestly, what’s so complex about it? :scream_cat:

But again, it’s just an interesting idea. I like to argue for it (because I do think it’s kinda cool) at least until somebody comes up with something that tells me it’s really not a good idea.

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Idk how I didn’t notice this until I re-read it just now.

It’s probs the best approach. It doesn’t help with (whole) lost coins, but that wasn’t the true core of the idea to start with.

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Well, It’s kinda like saying “you cannot carry your money, you must juggle it”

Plus you have to add all the software in to make sure people juggle, and each of the vendors has to verify the coins are still valid etc etc etc…

Cryptocurrency has a steep enough curve without adding the “you must juggle or you lose it” component.

I don’t see any significant benefit that would override that concern.

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Wallet apps have to do a crazy amount of juggling already; it’s almost no overhead.

Payments don’t follow a linear distribution: small payments are much more common than large ones. Something will be probably necessary to incentivise keeping coins in one piece, otherwise people will just start dividing their coins whenever they feel like, and soon large amounts will require a huge number of pieces to be added up together. This idea is just a possible part of the solution for that.

Anyway, if the expiry rates are calibrated well, and the wallets work alright, most coins (parts of coins, really) will be spent before they could get close to their expiry date, and the rest would get exchanged to larger divisions, thus gain a higher life span.

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I’m glad that there is no plans to do such with safecoin, but you might be able to create such a currency yourself using SAFE altcoin tokens. The only problem is that the SAFE network doesn’t understand time and, as far as I can figure, doesn’t even have a good way of establishing universal sequencing (a key element of time). This is problem with what you propose, though perhaps there is a way of handling this if you include some sort of oracle from off-network.


Very true. The first time I considered something like this, it was in the context of a currency based on a blockchain (well, a variety thereof), and it would’ve been based on the number of blocks since the tx. It would’ve limited the size of the data required to be kept around.


Well, that idea is misguided.
You can’t know how long someone has been holding a coin, and even if you could, Safecoin has no concept of time - all coins are same old/new.

Philosophically I’m with @chadrickm: don’t want no shackles on me.


Are you aware of how SAFEcoin works?

As of now, it isn’t divisible, and coins really aren’t combinable either. The coin lives in the network, and never moves, Only the owner changes…


You are well aware that future divisibility has been brought up a lot already.

The killer of the idea is what @fergish mentioned: the network lives in a world without an inherent concept of time; I foolishly overlooked that for a moment :scream_cat: