I think your lucky, I'd rather have it like that, people in real life dont "respawn"
This is why I hate terms like respawn because then some misunderstand what it`s supposed to be depicting.
Respawning bandits in dungeons is supposed to be giving the illusion of new people who have wandered by and FOUND a cave or ruin, seen that it`s empty and decided to make it their home or hideout. It`s actually a great way to add realism to the game and give Players something more to do instead of having a completely dead world after a bit of time. They are OCCUPYING spare space.
I am always watching for stuff like this as it`s particularly important for a sandbox world game- and I`ve played them since a long time, so i`m pretty sure I`d see the problem if it was there.
I still beleieve that this complaint about non respawning lairs is simply a stubborn misunderstanding of how the game works. I have just been back to Helgen and found new bandits there, just as I have other dungeons. I`ve tested and seen empty places `refill`.
I, and others have said it before and I`ll say it again. You need to stay away from a cell for 30 days (do not go out for that entire 30 days if you want to test for sure), then go look. Everything should respawn with quest things and character npcs possibly being the exception.
I did this test once already and I`m not doing it again because some people won`t accept or appreciate it- Test for yourselves. i`m not wasting my time again.
Now I`ll leave you guys to continue believing what you want to believe.