Absolutely muddypuddles. There is one that springs to mind – Ide Tunnel. Disabled for a very very long time after it went missing, then finally archived and disappeared. Within a week a new cache had appeared to honour the original and a great location.
It took me a little while, having been used to letterboxes, to understand the sometimes ephemeral nature and short lifespans of geocaches, but it definitely is a good thing in my mind. The system creates a shared responsibility that is often missing in many letterboxes (I’m thinking of the “kids boxes” that do tend to litter some tors which are left out and seemingly abandoned, not so much the registered boxes). Even with the maintained ones, unless found by a friend the owner won’t know of any problem until they go and check themselves.
(That said, I did get a FTF from a Geocacher on my only letterbox who recognised my nick, which had been out for some four months without a single find!)