So do NPCs' on-person inventories respawn after you've pickpocketed them?

Solution 1:

I was obsessing a little too much over this so I jettisoned my current playthrough and did a completely fresh install with no mods and experimented a little:

I stole everything off: generic NPCs, named NPCs, and followers both before and after I recruited them.

In all cases, if you steal everything off them, they will all respawn their clothes after 3 days. No one goes naked forever.

Both generic and named (non-follower) NPCs will not respawn anything other than clothes (as far as I can tell).

I tested this on Faendal both before and after he became a follower. Before he became a follower, he respawned clothes as well, but didn't respawn weapons. After he became a follower and we left the cell where I made him a follower (his house), he respawned his weapons again.

This is just a preliminary answer, I'll keep updating it as I find out more. I'd like to test it out for up to 30 days, and with a few other followers.

Solution 2:

This link, this link, and this link seem to imply that named NPCs do not have respawning inventories (Such as Jarl Balgruuf or Esbern), whereas generic NPCs (like bandits and guards) do reset their inventories after a long period. By stealing from a Whiterun Guard and Ysolda, stepping outside of Whiterun, waiting a week, then coming back in, my game seems to confirm this (I do have mods, although I shouldn't have any that affect this).

Assuming the above is true (EDIT: Which it doesn't seem to be, see comments), a simple answer is:

• Named NPCs never respawn (except maybe in a quest scenario where their inventory is changed)
• Followers never respawn (they are also Named NPCs)
• Generic NPCs do respawn

EDIT: Perhaps there are more checks to refresh inventories of named NPCs than I thought, or there could just be other rules in play.