If they die, they are dead, first point xD
Secondly you can retrieve all your stuff from their bodies. Mine died yesterday in a dungeon, my fault apparently. She ran into my shouts while taking damage from Draugr. So I got kicked out of the mage guild.
But you can get your stuff back, bodies don't go away, they stay there forever.
On a totally unrelated topic.
I hate the favourites system in Skyrim. It sucks ass!
I suggested to some modders to make a better system and hopefully we'll see something like that soon.
here's a mockup of what I want for the Favourites system.
