I think that the body doesn't really need to be asleep in order to rest or repair itself. I believe that the purpose of sleep is to replenish our mental energies. Of course I could be wrong, but I've found that in my life, the more in tune with myself I am (happy, passionate about something, eager to get on with my day every morning, and so on) the less sleep I need. Some nights I only go for 3 hours and yet the next day I'm as fresh as a daisy, ready to go again!