The beginning is very, very slow. It seems like the longer games are easier, when played on the same difficulty level, since you can war for longer without units becoming obsolete. Although this is the exact reason I wanted to play a longer game, it negates the AI production bonus, when you can use the same 15 city raider 3+combat promo swordsmans, without having to start building macemen. Once my city raider swords were promoted and had proper escorts (Catapults, shock axes and formation spears (phalanx in my case)) they steamrolled the AI without any loses. Perhaps kicking the difficulty up a notch when playing a marathon game is the way to go.