I'm not sure what exactly do you mean? The point is to balance production with retrieval/runners. If you have too many ores on the screen, then you need to buy more runners and upgrade them further. Or buy other protection such as turrets so they get stunned less often. Though in the very late game, especially after level 40, when you have a massive army of attackers, it is possible they might not be able to handle all the production. However, I am planning to add two additional units responsible for collecting ores; Bulldozers and Stonecallers. Those should help a lot too.