I'm 31 (32 in a few months) and for my sleep... Honestly its random.
Sometimes I'll sleep for 5 hours, others 7 hours, even go as long as 17 hours.
It mostly depends on how active my mind is prior to me going to sleep, if very active, I'll be awake in 5 (or less) to 8 hours. If I was extremely bored & had very lil to do, then I'll be down for 10 to 15+ hours. Also how long I stayed up also helps with the extra sleep bit.
Also, my sleep schedule is constantly changing - I never go to sleep at the same hour & I never wake at the same hour, my internal clock is always going a few hours ahead every night (most times of my life I'm a night person). And I've tried to keep a specific schedule, never works out.
Oh an just in case, longest I ever stayed up without really noticing til I started to count from the last time I slept: 96 hours (even done this with my eating habits, forgetting to eat for that long).