I often wake up lots and go back to sleep. The longest time I've been asleep uninterrupted was probably when drunk/hungover and for around 12 hours. It doesn't happen very often, as I usually stay with friends and we get up to go and get a greasy breakfast to make us feel better!

I don't like sleeping for a silly amount of time, I feel like the day is wasted. Even if I'm hungover I find the best thing to do is get out and do something to take my mind off the fact that I feel terrible!