The answer is different for each vehicle.
Ball joints are a consumable part and they do need to be replaced.
Everyone drives on different terrain, with different size tires, and every driver has a unique way of driving into the turns and braking this all has an effect on the life of the ball joint.
Were the ball joints greased and maintained on a regular schedule or were they never greased?
Did you use high-quality automotive grease?
We have customers that do not grease the ball joints and bushings and they do not last long at all!
We do have some customers that had 100,000 miles on a set of JBA ball joints. Not every application will have these results.
We have a 1-year warranty on the JBA ball joints for the fact that there are way too many variables that cause a ball joint to were that are out of our control.