Bearings are either perfect or they need to be replaced. They do not wear. I don't know how people here got the impression that bearings need to be tightened. They should be designed in such a way that the clearances (or preload) are reasonably maintained during the life of the bearing. If people are experiencing loose bearings, then they were either improperly installed or something is systematically happening to the mount surfaces causing the races to shift. Bearing problems are not cured by tightening.
95 E320 Cabriolet, 131K