I went a little over 200K mi. on my 300CD's steering box, however, by that time, the car had become laborious to steer and the steering wheel certainly didn't return much after turning. I just tolerated the worn out box until I decided I was ready to spend the $s and replace it. The car was *much* nicer to drive with the new steering box. Of course, many of the front end components had also been replaced recently...