But not too long for most. I've done a fair amount of reading about sleep. Obviously there are many that can thrive on 4-5 hours of sleep, but 8 hours or more is what the majority of people need.

Me, I try to get 8 hrs. a night, though I think I need more. I can get by on less than 8 hrs. but if it happens a lot it catches up with me and I'll need some extra sleep, whether it be a daytime nap or a longer time in bed at night.