CBDCS (central bank digital currencies) are the worst possible use of blockchain, and where the world is currently headed. National banks will attempt to preserve their ability to arbitrarily print unbacked notes (debase currencies) at will. But worse than reducing their value while artificially funding their tyrannical pogroms, they would love to be able to expire them. This is much different than the "expiration" of offline cash notes. Offline cash notes can empty the btc to any digital wallet throughout their lifetime, and, upon maturity, the holder of the note doesn't even require a second signatory to do so. CBDC notes, on the other hand, will not allow redemption in any form. They will literally expire. No backing.