Yusuf: Brain function in the dream will be about twenty times to normal. When you enter a dream within that dream, the effect is compounded: it's three dreams, that's ten hours times twen...
Eames: I'm sorry, uh, maths was never my strong subject. How much time is that?
Cobb: It's a week the first level down. Six months the second level down, and... the third level...
Ariadne: ...is ten years! Who would wanna be stuck in a dream for ten years?
Yusuf: Depends on the dream.