[misnome]

Right, the reaction wheels help if you want to maintain orientation of the satellite under external forces that want to (gently!) rotate it. And eventually your reaction wheel saturates and you can't get more useful rotation out of it.

This is where thrusters are useful, because you can use the thrusters to give you a "source of force" while you spin the reaction wheels back down. I believe this is where the original parent's question is coming from - if you have no thrusters, how do you avoid saturation?

Presumably, they've worked out a way to accurately predict the external forces and gently operate against them while spinning the wheels down in a way that doesn't make the satellite spin faster.