Both games lasted a long time (one was in person for 10 hours before we ended it, the other was an online game with one turn made per week). Both times I was completely crippled (if someone is going to betray you in Diplomacy they better cripple you or they're going to be fighting multiple fronts later, and that's really hard to do in Diplomacy), and had to basically observe what happened for the rest of it.
I still stand by my statement. It's just a game. Just because it took a few extra hours than most doesn't mean it should permanently damage friendships. Maybe take a week or two break from everyone to decompress from the absolutely intense and crazy experience, but not permanently damage a friendship. That's the sign of a very weak friendship, I feel.
As for more at stake...what's at stake? A 'yay, I won!'? It's not a poker tournament where the winner is going to take home $100,000+.