I've set up about 4 custom games that were 9+ hours against AI by going 1v1 on Steppes vs an easy AI. They will NOT cap the map whatsoever until you start exploring the map, by then you will have 9999 of every resource. I have had a couple of bulletins drop for the new factions but that's about it. I think you're better off just playing real matches.
P.S. the current system sucks ass.
The idea is to do it while you're afk or attending to other matters on the computer. Maybe I'm playing 2048, browsing this forum, and watching some YouTube videos. In the background, I'm also winning war spoils