Let's not lose any sleep over what the "experts" say:
How much sleep do you really need?
Experts generally recommend seven to nine hours a night for healthy adults. Sleep scientists say new guidelines are needed to take into account an abundance of recent research in the field and to reflect that Americans are on average sleeping less than they did in the past.
Several sleep studies have found that seven hours is the optimal amount of sleep—not eight, as was long believed—when it comes to certain cognitive and health markers, although many doctors question that conclusion.
"Question that conclusion." In other words, they don't really have a clue.
This is one of those areas in which it is intersting to pay attention to the research as they zero in on the probable "right" answer, but it's not something we should rule our lives by. Most of us, I think, can figure out what the optimal amount of sleep is just by noting how well we feel after certain amounts.
As it happens, seven is about right for me, although I have gone through periods when I average about six. If I stay in bed for nine hours, I feel groggy and befuddled most of the morning.