AI War:Resource Caps
Are There Resource Caps? What Happens When I Hit Them?
A: Yes, there are caps for Metal and Crystal. Each will stop at 999,999 stored. If you are playing multiplayer, the surplus will be divided evenly among your teammates. If you are playing alone, the surplus is simply lost.
Either way, if you're hitting this cap then either things are going really well for you (are you playing on an appropriate difficulty for your skill level?), or you're not properly managing your fleet production. Don't forget to have lots of Space Docks, and to have them loop-building so that you don't have to manage their individual production queues yourself!
In newer versions of the game (Post 7.11), Crystal as a resource was removed entirely, with all ships now costing various amounts of metal and energy. Fortunately, Command stations and select other structures (Especially those in the fallen spire campaign) now provide a static bonus to your resource cap, so as you expand you will be able to collect more resources, allowing you to rebuild fleets more quickly.
Hacking, the new resource as of 7.11, has no cap.