I’m a big fan of federations with explicit expiration dates. I really hope this becomes normalized behavior by mints and users of mints. 

It does bring up all sorts of interesting convention points around how to ethically and/or legally turn off a mint. Should deposits to the mint be turned off days/months/years before its shutdown? How many days/months/years should users of a mint be given notice before shutting down? Etc, etc 

 Excellent points I've never even considered! Stoked to see how this all plays out