The bigger the empire, the more likely it goes into revolution. Many a game looked like I was stuck then, boom, chaos in the neighboring empire. Waiting might be key but going after Egypt probably more fun.

PS - currently playing Med II - a few things like movement, fighting on the walls, and how the Pope is handled I like better but they truly dumbed it down; I miss revolutions, six month turns (each season is two years! - give me a break!), returning kingdoms when a "lost" heir returns, and new AI kingdoms (Switzerland, Burgendy, etc.). The Mongols still follow you all over the map though - would have been nice to fix that.