I play a lot of games against AI 4v4. I love the Rivers map because it has water without having a focus on naval battles. I usually create trade fleets to earn gold.
I would love if the AI could also use trade ships on Rivers maps to keep gold inflows coming for them so that the games can last longer.
I suppose AI should also use trade ships on the other water maps also to gain gold.
You sure know how to get the most out of an AOE game. Maybe the devs will pickup your idea. In the meanwhile you could also donate some excess of your gold to the AI. Yes, that is a possible strategy to stretch your current games even further. Do you play 4x4 on hardest?