I am not sure about this, i had periods of 5h a sleep days for a week or two and then slept 12 hours for a day and felt very fresh and carried on with 5h a day. Sometimes it's 7-8 hours a day for couple weeks, sometimes it's 5. Feels about equal to me, maybe it has to do with volatile working hours for me, not sure. All I know the worst is hangover days and on holidays I stay in bed for 10hours only to feel unusually tired. Maybe environment is a bigger factor than genetics.