Of course that is less aggravating then finding an abandoned city, where all the deadbolts are expired etc, and then finding a few chests still there deadbolted by someone who still plays but has long since left the city. Irritating.
Perhaps they can expire if you don't go within 12 chunks of them for 20 days?
Maybe a list of shops/chests which were used in the last 30 days.
If shop/chest is not on the list would lose its protection (note that this would need an initial 30 day phase where the chests are recorded but not unlocked if it is not).
Altough I have to admit that to make this fair you would need a command that tells you if within x (maybe 3-4) chunks there is a chest that you havent touched for 20+ days as a warning).
Results of this would be:
-Player is gone but had shops -> unlocked after a month
- Player left the region but is still playing -> unlocked after a month
- Player still has uses for chest -> can see when they are near unlocking and just open them once (every 30 days, which I think is a reasonable large amount of time).
Altough this ^ is just a concept and would require coding , making it less likely to happen
OR
you copy the following line when you find a shop of an inactive person:
/t c I found a chest shop of a player who is inactive (20+days) and want it unlocked please.
After someone took the ticket you should either stay by the chest or give coords (including the continent) of the chest + name of the owner and ask them nicely.
Considering that inactive means you forfeit your fac and your deadbolt it should also count for your shops.