Originally posted by Kestas
Bearings do not wear in the conventional sense. Any increase in clearances is the result of additional seating that occurs during use. If a bearing does wear, then it is experiencing a condition that will eventually lead to failure.
The bearing itself does not wear, but the shoulder on the spindle that the inside bearing inner race rests against will wear/gall, especially if the car is subjected to a lot of cornering loads. The spindle shoulder wears rather than the shoulder on the bearing race because the spindle material has a lower hardness, and this wear is what causes clearance to increase with use assuming that the bearings themselves do no spall.