I am having some doubts after reading that a one-time purchase would grant a user a fixed amount of storage for eternity. I fail to see how this would make economic sense: providing storage incurs an ongoing cost (hardware, electricity…), which cannot possibly be covered by a one-time fee of any reasonable amount (short of a sum large enough that it could be invested, and the proceeds pay for the ongoing service).
I understand that storage is and will keep getting cheaper over time, but in order to compensate for the lack of recurring revenue, the cost would need to converge toward zero (e.g. halve every year) at a consistent rate, forever. Nobody can predict that this will be the case.
I believe that to be viable, SAFE storage must move from a purchase model to a rental model. Otherwise, the cumulative weight of storage that has been purchased over time will eventually offset new revenues, and SAFE storage providers will abandon the network. Or the cost of new storage will become prohibitive (in order to pay for the existing one), and new users will balk and abandon the network (or switch to a newer, younger network that does not have the same liabilities).
This rental model, by the way, would also be the only way to keep some degree of efficiency in the network, letting old data that is no longer needed or wanted simply expire.