I often find myself with 900k cement, while 400k steel. Sometimes I have more of one resource than another, and they max to the limit and i can not do anything to lower them untill im done building/training ect.
I suggest a marketplace where you can trade certian resources, either through AI or other players with a 3:1 ratio.
If I want 500 steel, I could exchange it for 1500 cement or food.
Anything with cash is a 4/5:1 ratio.
500 Steel for 2000-2500 cash.
That way you will lose profit, but you can prevent maxing out resources and not being able to lose efficent progress.
I would use this marketplace only under circumstances where.. If my max limit for all resources was 100,000.. and I had the following..
I would exchange about 30,000 steel for food, adding 10,000 food leaving room for all of my resources to efficently gain again.
Well thats about it, thanks for reading.