In brief, the basic argument is that rather than rotors warping, the brake pads deposit microscopic bits of themselves on the rotor ( Brake Pad Bed-In
). The run-out or "warp" comes from these deposits not being uniform around the rotors surface. The article I linked to above explains it in great detail as well as methods for prevention.
This information does not answer the OP's original question, but I offered it hoping to debunk the common thought process...and possibly prevent him and others from needing to replace their rotors before they otherwise should need to.
'04 GMC Sierra 2500HD, CCSB, D/A, MaxBrake, B&W Companion, Retrax Pro, AR Power Steps
2013 Rockwood 8289WS w/Diamond pkg
1969 Camaro RS/SS Convertible
Dad's old 1968 Empi Imp (recently recovered from under 21 years worth of boxes/dust)