You need to explore around. There are very rich fields far away from your base. You need to setup outpost with train delivery and that'll allow to run for a ver

You need to explore around. There are very rich fields far away from your base. You need to setup outpost with train delivery and that'll allow to run for a very long time before those fields will expire. And then with bots it's just a matter of copy-paste new base and connect it to your railway system.