BMW Repair: BMW 323i bake discs, bmw 323i, driven 3

Question
The light signalling that the brake pads were finished came on and we brought the car to the dealer the next day.

They changed the front discs and the brake pads. I thought that it was kind of early to change discs as they 1/ looked great - no rust or pitting 2/ car was 80% highway driven 3/ the mileage was only 13,000 miles.

The service department replied that it was standard procedure to change both discs and pads when a car comes in due to the fact that cars now a days have ASC and as well they said the discs were worn.

I have a hard time believing this. Do discs have to be changed everytime pads are changed?

How can I be sure that discs are within tolerances? What are the disc tolerances and can't BMW discs be turned?

Thanks,
Henry

Answer
It is standard procedure to replace the disks with the pads.  You could just as well had the pads only changed, i'm sure you can goto a corner shop somewhere and have Bubba turn the rotors and it might be OK. BUT, you own a performance car that has higher than normal safety and quality standards due to higher performance.
I don't turn rotors, it tampers with the heat temperment and can lead to premature heating and inefficent cooling.
But, thats just the opinion of me and all the mecnanical enginers at BMW.  What do we know?
-cheers