You can select 3 levels of difficulties for AI (easy, medium and hard).
When you see enemy you should have good military strength on a border. It means enough of fortresses for example. Then enemy will not attack you. This is my experience.
I am ready to play with you if you want.
The best time for me is evening usually about 19:00.
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Martin (DMM)
It is never too late to start play RttR!