Might want to get the car checked out. My mom drives a G55 which is equipped with slotted OE rotors and has never had a warping issue with and she is far from nice or gentle with it. From the time it turns over it's run hard and there is no cool down period either. Did MB ever warranty them? If I recall they usually only last about 12 to 15K miles, I think on the AMG tuned cars you replace rotors when pads are changed for max performance.