How do you know you need a new wheel bearing?
If its 10k miles or more with original bearings, you likely need new ones. They are not the best to begin with, being sealed only on the outside, and age and condensation will rust them even with little mileage.
If you have it apart, stick your fingers in the inner races of the bearings and turn them and spin the wheel. If they feel crunchy, guess what?
having said all that, I've put many more miles on them than that. THey seldom fail outright, they just get crunchy.