The Uniball should be replaced when the ball shows a wear ring around the center where it contacts the fan hub. As long as the ball is round, it can be reused. I find that if the dampers are replaced before they are totally ruined, the uniball is usually still workable but if I have ANY doubt about the ball, I replace it as if it is worn, it can detroy the dampers and the start shaft bearings, costing way more than replacing the ball.