I think Emperor being an almighty 1000 years old Sith is plain stupid. I don't know how can any writer come up with that kind of crap. It is insulting to the Star Wars universe.
I just go with the theory proposed in Annihilation book that Emperor has always been just the most powerful Sith from Dark Council.
Insulting? Palpatine and every Sith has wanted immortality forever. Someone was finally sucessful, and boom.