I doubt that a loose ball joint could cause premature brake wear but there could be others that disagree with me.

Brake wear can be caused by many problems, but I'll ask: what type of driving does the vehicle see? A lot of highway miles? A lot of in-town? Combined?

The way you determine a bad ball joint is to support the vehicle on the frame with the tire off the ground. Then, using a large lever, for the tire/suspension assembly upward. In a bad joint, you will see movement in the joint prior to the upper control arm moving.