I usually need 10-14 hours to feel good. Less than that, and it's impossible to get me to wake up. I've skipped school and been late to work soooo many times just because I don't have enough sleep. :(
I take naps alot if I get less than 8 hours.
Staying up late is the main problem. I usually go to sleep past three and wake up everyday around 2:00-2:15
I used to be a big sleeper with 10 hrs a day uptil university in Karachi. But then in UK it got to 7 hrs plus minus and now at work with family its 6 or sometimes 5 as well.
I think I am quite used to it now. I can still sleep 10 hours but rarely get chance for it. And I dont regret it either. I enjoyed it when I had time but now I have got other responsibilities. For example my wife woke me up at 8.30 yestarday when I was dying to sleep as it was off, but had to wake up as there was urgent and importat stuff to be done. And I had no chance to sleep all day till late at nite. It's life.
Am I grumpy after 6 hours sleep, hmm not really or may at times but once you are over with 20-30 min phase in the morning at work its gone till next day.