At the moment I can't sleep more than a couple of hours without Olanzapine (Zyprexa) as I am hypomanic. My pdoc recommended I take the med at the moment to at least get 6 hours sleep a night as the more nights you go with little sleep the more likely your mania is going to intensify.
When I am depressed I find it difficult not to sleep and often get 12-16 hours a day. When i am wonderfully normal (a rare event) I tend to be happy on 7-8 hours. Along with all this I do several things to try to aid my sleep such as regular exercise (I swim), meditation, regular waking and going to bed times, healthy diet etc