I think we have the second highest turn count with this game that is still currently going:
http://warlight.net/App.aspx?GameID=1001356
This one is currently at turn 521, and the game started on March 10th of 2009 which is about to break the 1.5 year mark.
I unfortunately got eliminated at turn 405.
I know you can't see any of the action yet because of the fog, but from the chat, it looks like the game is just about to wrap up.