I slept 9 1/2 hours a couple days ago which is unusual for me and I couldn't kick the head fog until like 5pm it sucked. I generally get 7-8 hours if I get much more than 9, which like I said is rare, I feel all spacey and thrown off for a good portion of the day.
I can't even think the last time I slept 10+ hours but I guarantee I was either sick or extremely hungover that's the only time I sleep that long.