It is proven though that 8-12 hours (though I heard 8-10, not 12) is healthy for you to gain a restfull sleep. After that time period, your brain has to work while you're unconcious to keep itself that way if the desired action of sleeping continues. For people that naturally sleep longer than that (sleeping more than 10 hours without an alarm to wake them), then it is because their bodies just need more, probably to recover from a lack of sleep. For people who sleep less, their bodies are just hyper active (aka. insomnia) or they're too restless to be able to fall into a restful sleep.<br/><br/>At least, that's what I think and all, however little it's worth.