Tony ten Kortenaar

I recently had the upper and lower control arms on the front suspension replaced by the dealer. I had complained about a creaking noise and wanted it checked out while in for an oil change recently. It turns out that ( according to the mechanic) that the noise was due to excessive play in the control arms.Has anyone experienced this similar problem? I own a 1997 A4 2.8 Quattro which I have really enjoy, and have had since new. There are 86000kms on the odometer, with the majority of these from highway driving.
I must also add that I have gone through a number of O2 sensors as well since owning the A4. Is this also normal? I appreciate your feedback. I have been a member for a few months now.