Imho this scheme would only make sense if the wallet software that holds the user's tokens gets automated to do the periodic "bankrun". It would be unacceptable if the tokens have a "expiry date" because the user misses the deadline to exchange tokens to the new epoch-keyset.
Discussion
Wallets do that already. Tokens can't have an individual expiry date because that would make them traceable. You can hardly miss a deadline because multiple inactive keysets can coexist for a very long time.