Bhav
Ive done many 12+ hour gaming sessions.
Also stuff like watching the LOTR extended trilogy back to back.
And now I also have a £300 chair that is even more comfortable to sleep in than my memory foam matress and contour pillow, and causes extreme levels of bliss when sat in all day long.
In the old days of EQ ... Saturdays and Sundays were reserved for huge raiding sessions of very large groups that normally took about 8 hours. WoW had much of the same thing at the start, with 40 players which was half of what EQ was doing. Molten Core, at the time (12 years? or more) took 8 hours on Saturday and 9 hours on Sunday to complete.
The issue I have with that kind of gaming is that it should be done as a "team" so you can switch out people and keep them fresh, thus the design of the tournament is pathetic, stupid and sadistic to say the least.