Whoah I'm a little confused partially probably because my conjurer is only at expert level conjuration so far but I just read the first 2 or 3 posts and don't understand.
I know that thrall's come from the master level rais dead spell and can be reanimated any number of times but leaving bodies in a house for 10 days? wouldn't they jsut disappear or are you talking aobut leaving active thralls in a house?
It's been my experience that undead don't always even follow you through a area transition from say a cave to the next section of the cave.
The vast majority of NPC , both named and generic , are temporary as you say.
They will typically vanish after a short time if you leave their cell (inactive)or during transitions(active).
Hanging on to a temp like this can work for a while if they are kept with you continously with some remaining longer than others.
But there are certain NPC who do not reset or respawn EVER ( at least under normal circumstances) and these are safe to leave anywhere for any amount of time.
As to why this occurs , apparently these do not have a respawn or Clean-up(assigned to coffin) script so their bodies simply have no place to go.
Patches to the game (applied after the events of my earliest posts) have greatly reduced the respawn time period (from 10 days to just one) for a lot of the temps and have provided clean-up for many others(notably Orcs from strongholds). Most disappear now with only a very few who respawn where you left them
So it`s kinda like the difference between driving your own car or joyriding a stolen one. the former can be parked and used again while the latter is just left behind after you`re done with it.
Permanent powerful corpses include Orchendor , Umana , Silus Vesuius , Arondil , Sulla Trebatius , Kornalus , Anska , and Anise.
Many other permanents of varying degree of power include members of the Khajiit caravans , Velekh Sain , and others right down to level 4-10 Citizens such as Seren , Lami , Fastred , Narri , Mathies , Captain Lonely-Gale etc.
For some , they will remain permanent so long as you don`t finish the quest line they are in , thereby avoiding invoking the clean-up script.
Haldyn(Rise in the East) , Escaped Criminal(companion`s radiant), and Wyndelius Gatherian fit into this category
Certain groups also appear to be permanent ( at least some of them) including Bandits from the Nilheim site and Mistwatch Bandits.
Many corpses that you find already dead(never lived) are permanent but they are extremely weak thralls due to low or zero health.
I`ve seen another Thrall thread where many who wish to play the game under the old rules simply refuse to patch or add Dawnguard DLC so they could do the things I related in those earlier posts. I might have done the same but my game was so bugged it had become unplayable without patching