We tried a few different setups, but they always ended up getting lost. Occasionally this meant they just dug a hole (which we could follow) until they ran out of power, but the ones we tried to use to harvest our essence crops on the surface would run off without reason. Once, one of our harvesters ran off to the next field over, and it took up residence there (causing issues for the one who lived there originally). Once I watched one run off into the sunset - I followed him for a long run, as he burrowed his way into a nearby mountain before running out of power. On more than one occasion, I would log in to a few holes in my house, knowing that the robots had gone AWOL again.
Golems were a welcome change, even though we had done that setup many times before. As derpy as Golems can be, they simply work most of the time. Hopefully you have better luck. If you figure it out, I would love to see an overview of your setup for reference.