I do install new bushings anytime I remove the old ones. The reason for not removing them until they are worn, is to prevent wear in the bushing bore in the transmission case. I feel it is worth they extra wear and tear in the bore to get rid of the debris that collects there. The bushings can be removed and installed several times before wear in the case is excessive. Then application of Loctite Bearing Mount works fine to secure the bushings and prevent leaks.