Originally Posted by GregW / Oregon
Rotors are replaced when they approach minimum thickness (which is stamped on the center). Typically, they will last two sets of stock pads, but your results may vary.
That has not been my experience with BMW service. I was told by my SA that they need to replace the rotors each time they replace worn out pads. (No he was not trying to squeeze cash out of me since it was done under the service plan in my previous car). Plus, it is hard to believe rotor "thickness" would be the only servicing criteria for rotor replacement. One would think heat cycling would have adverse effects as well.