A staple in many modern RTS's is for the resources, whatever they be, to never fully be depleted and resources to become technically infinite.
- In the Tiberium/RA C&C series, a Tiberium/Ore field can be depleted but will slowly regenerate if left alone for a while.
- In RA3, specifically, resource nodes would provide much less to their harvesters if they were depleted, but would still give something.
- In C&C Generals, each faction had an alternative way to acquire funds outside of the normal supply depots.
- In some games like the AoE series, you could trade for resources you need, with Gold being something you could get infinitely
I'd like to suggest that we follow in the stead of RA3, with Oil Derricks giving a highly reduced load to harvesters after they've been fully emptied. So, that way, you are still heavily incentivized to expand and conquer nodes, but you're not entirely screwed over because you emptied one. You'll still get a very slow trickle of something.
Another alternative is to go the Generals route and give every faction an alternative, passive form of income, one that pales in comparison to harvesters (and probably locked behind the Armory or equivalent), but is reliable.
Granted, I do realize that "infinite" is an option, but that's just infinite resources at normal harvesting speeds. I'm suggesting infinite resources at a highly reduced speed when the node is emptied, so that you can't theoretically get stuck because some AI player sent all their harvesters to your nodes when you weren't looking 😛
