If a key is requested from a mob, will it ever come back or do you have to wait until a reboot (or someone else kills it)?

For most areas, you have to wait for a reboot or for the mob to die. There are a few that will come back on their own though.

Pro tip: Check any pits nearby (Wood-elf hometowns are pretty commonly used). A lot of players like to drop keys in pits so they can re-use them later, since pits survive past reboots.

http://forums.carrionfields.com/dc/dcboard.php?az=show_mesg&forum=3&topic_id=436&mesg_id=436&listing_type=search

Requested items SHOULD come back, it just takes a reasonably long time.

At least, not sure it works for non-worn keys.

Area I'm thinking of is an area explore that has, well, a LOT of keys. Those keys seem to be out for a very long time, while other areas with worn keys (ie, Eil Shaeria) they do definitely repop eventually

Yeah, Java is right, it's not working this way - keys are not coming back to mobs who normally have the key in inventory. Checked several times over hours and then days.

Was certainly this way in Elven Vaults, keys never repop on NPCs that I ever recall. But then, I think maybe it does work in Organia, so it seems to vary by area and maybe authors had a degree of control over it.

Since there is a system wide reboot ever 48 hours (or is it 49), I wonder what the intended key repop timer is supposed to be. RL hours I assume.

Or held, at least. Can't remember which.

I did have something of a suspicion that it was possible there's a difference in worn vs. inventory. There should be no difference between areas that I'm aware of.

I will at least bring it up, but whether it's major enough to be a high priority (if there even is a discrepancy) I can't say.