On Call of Duty: United Offensive, I was involved in a game of Base Assault. I got bored after about 1.5 hours and left. I came back 2 hours later and the same damn game was still going on. I was able to get in there and help plant the last dyno and defend it luckily. I think total time for that round was close to 4 hours
edited to add: The map was Kursk, for those of you who play CoD:UO