For anyone who hasn't played Diplomacy, it's a very interesting game but can take a very long time to complete. There's a round of negotiation where you can meet with other players and coordinate moves, then all moves are executed at the same time. Much of the length of the game is dependent on the personalities involved and any rules you apply to limit round length.

I started a game at 7 PM and left at 4:30 AM. None of the players had been eliminated, but we all had a great time backstabbing.