I'm 22 and about ten hours is an ideal amount for me. I'm able to function on much less but I'm not usually happy about it. I've noticed by body definately needs more sleep now that I'm not a teenager anymore.
If I'm in extreme circumstances I can easy go without sleep for about 40 hours before I start craving sleep.
If I'm in extreme circumstances I can easy go without sleep for about 40 hours before I start craving sleep.