The longest that ive slept all the way through was 18 hours, the reason for that was i missed the previous nights sleeps because of staying up night fishing for eels.
Let me see, i guess I have once sleept more than 13 hours! But, only once! Now, less than 6 hours a day!
Longest I ever slept was for 16 hours. I was actually sore from sleeping so I needed to lay in bed for rest of the day. Kinda funny