I need my 8 hours of sleep, minimum. I feel great after 9-10 hours. If I'm woken by an alarm, it can be out of whack with the sleep cycles and I tend to feel quite average. I love a long sleep where I wake up without an alarm and feel refreshed, alert and strong. Additionally, the more hours I get earlier in the day, the better I feel. I remember reading something about pre-12:00am sleep being of extreme importance. I think it was Ian King?