They don’t ware down. They get pushed down when the bushing is not lined up properly. If there isn’t room to go down, they can distort the bushing causing binding and leaks. Any movement of the bushing will cause ware in the softer aluminum. That is the reason they are pinned. If broken off below the surface, drill a new hole to the side of the old and put in a new pin. . . . . 😉
