Have you ever sat at a D&D table and fought a large battle - you'd probably be there 3 weekends running, LOL.
Seconded. One recent encounter lasted several hours and meant nothing in the grand scheme of things. I had a quiet and constructive word with the GM about that one.
Mind you, it was nothing to the combats we had using Hero System. Now there was a system that cost the players as much fatigue as the characters.