320i 2004 replacing front ball joint at 45,000km's

Hi!

After the Stability control light coming on only at cold start, it finally came on and stayed on. The local repairer is relacing something on the central steering under warranty (as should be - car is less than 3 years old)

But they have also found a problem with the "ball and arm" joint on the front drivers side. He also called it a "basher"? He said that this is a part that is normally requiring replacement at 60-70,000 kms.

My question is whether I should fight this replacment (they are charging me) or should this be a manufacturer warranty issue, considering milage and age of car? This car is only city driven (short trips under 40kms)