I actually sleep less when I'm hypomanic than when I'm manic.
Strangely enough, when I'm manic - I sleep about 7 hours. This is only a few hours less than my pre-medication self. I usually really burn myself out when I'm manic (intense exercise, floor pacing etc.) and have difficulty sleeping, but I usually get to sleep and stay asleep for a long time.
When I'm hypomanic I sleep 4-5 hours and spend most of that time on my computer doing work etc.
Do you sleep normally during your manias?