The longest as a child was something around 5:30 AM on New Year 1995 (I was 7 back then). We celebrated in a neighbour's house and I can still remember how I totally didn't want to go home yet at around 5 AM.
Then at the age of 12 we went on a ski holiday and I was so excited that I couldn't sleep the day before (which was the last day of school so I stood up at 7AM). But on the first day there, after some hours of skiing I was so tired that I fell asleep at 5 PM which I think is the earliest time I ever went to bed (if one doesn't count "siesta" etc.). And I slept until 9 AM of the next day, yes, 16 hrs, which was probably my longest sleep.
2 years ago I got up at 10 AM the one day, couldn't sleep the night, had an uni course the next day at 8 AM and in the evening helped at some kind of village festival until 2:30 AM, so I got into bed at 3 AM, that was probably my longest (41 hrs). The strange thing here: I was really tired in the morning and afternoon of the second day but not at all in the evening...