When I was a Junior in high school, I was in an engineering program that lasted 3 weeks on a college campus (McNeese State). The program was named "Young Scholars." Anyway, all of us worked our asses off with little sleep (we averaged 3-4 hours of sleep/day). When the program ended, I arrived home at around noon on a saturday. I went to sleep and woke up MONDAY night around 7pm.
I do remember getting up one time to use the restroom. Other than that, I slept straight thru. So, my record for sleep is an astonishing 55 hours. I woke up feeling refreshed.