I work for the bearing industry in a technical capacity. Improper installation is the main reason bearings fail in automotive applications. When looking at warranty returns or failure rates in the field, there is always constant friction between the bearing manufacturer and auto (or truck) maker. The automaker is always saying "You make lousy bearings". The manufacturer replies "Your service departments don't know how to properly service bearings".... and the beat goes on. That's why the industry has trended toward preloaded, non-serviceable hub units, which cost ten times more to replace than the previous design.

Setting proper preload has the most important effect on bearing life. All this anecdotal shadetree advice of setting bearing preload followed by "... and never had a problem" probably didn't follow how long the bearing last beyond a couple years. Properly serviced bearings should outlive the car, and should definitely outlive the non-serviceable units that are commonly popular.

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95 E320 Cabriolet, 169K