Read up:
http://www.stoptech.com/whitepapers/...otors_myth.htm
Ask any *well educated* brake tech and they'll point out that you can tell if a rotor is warped by simply spinning the spindle with the caliper on and measuring the clearance. Since learning this I've watch mine and my friends' cars rotors I always assumed were warped never were. An engineer friend was quick to point out that similar metals are used to transport and pour molten metals... and those containers go a long time before warping.