Does anyone know what this means?

In the UESP wiki the dead thrall page discusses something called a Permanent Thrall Corpse. Does this mean the corpse will not disappear if left for a long time?

http://www.uesp.net/wiki/Skyrim:Dead_Thrall

There is a lategame Conjuration spell called Dead Thrall which means if you cast it the body doesn't vanish in dust, but if you cast it and then your thrall dies and you leave it for awhile the body will eventually be deleted by the game, I'm sure of it, but I DO believe there are spots where corpses don't vanish and I think some people store their thralls there.

I am not certain of the locations myself though, but I have heard its player housing etc, but not 100% sure.