I have played 6 games.
My first game lasted until Britain fell, about 7 hours.
My second game was 4 hours.
My third game was 4 hours.
My fourth game was another 4 hours (against the same person.)
My fifth game during the superbowl lasted 2 and a half hours (Allies fell) and
My sixth game had no clear victor and we called it quits when they kicked us out of my old elementary school (7 hour game.)
We play with all normal rules besides we play World Domination and Russia doesn’t attack on first turn. The next game we play, we plan to put aside and continue it to the bitter end.
The longest game I heard of was over 50 hours, and America won.