My longest session was probably upwards for 15 hours. This was years ago on Absolute Poker. Can't remember exactly, but I think I was up close to $2000.
4 years ago i start with satelites at Titan Poker from the morning with 0.33$, i won 5 satelites to can go to the main event where i played 7h+ and i was 9th from 1200 players
live 7 1/2 hours in a tournament - plus driving time 3 1/2 hours. Won $3000 so that was great but was had it at the end and needed a black coffee to get me home. At my age 70 mumble mumble a great effort but thought it was rewarding. Got home and showed the wife the result (error?) - she was pleased and said - that will pay for our trip to Perth (Australia) - we live in NZ. Oh well enjoyed the money for a couple of hours.
I like to play tournaments and that's why I play in general for several hours. My longest play was about 8 hours. Every time when I register to a tournament I check my freetime. I think the one of the worst feeling in poker is that when you have to leave the tournament because of a very important thing.