The bearings in our purple upper shock mounts have a lifespan of many years, but they may eventually need replacement. Symptoms are a rattling noise from the top of the shock and a bearing that can be easily turned by hand.
These bearings are built to a very tight tolerance for maximum life - if you install a typical spherical bearing, it'll wear out in a matter of weeks. Replacement is fairly easy, although the bearing is a press fit in the body of the mount. You will need to transfer the stainless bushings from your old bearing to the new one.
Sold individually, one needed per mount.