As the bearing are lubed with oil rather than grease, I would assume that they need to be relubed more often than greased bearings. I switched to a full set of Avid bearings after I got some thread lock into a bearing when I maintained the car after one meeting, so I cannot really comment on how well the stock bearings last. It is not that I felt the other bearings needed to be replaced, I just had wanted to try a set of the Avid stuff for years.
