How to beat moderate IA?

I want to expand on this question, I can beat the IA in this difficulty BUT it takes me a long time (50-60 min) and I need to always survive the first two massive waves, the IA produces a lot of units and in order to defend, I use castles but somehow I feel that is cheating.

What are your thoughts on this? how to beat the IA in 20-30 min? no rush.

I get to feudal at 9:30 and castle at 18-20 min.