Once I raise bonuses I don't drop them much. I'm at full bonus for cup and CL and half/3/4 for league. I sometimes drop it to 1/4 against bottom feeders with really bad teams. Once I raise it over half, I never put it to 0. That's how you get troll results and get blanked and get sub-par ratings.
We are referring to the training bonuses of the new version. If you are still playing the old version, you may not have seen them.