A few possibilities with this problem.
First, make sure you match the pad with the rotor in compatibility. If you use very hard pads with a "softer" rotor, you can get rotor warp. The best bet if you aren't gonna upgrade with matched aftermarket components is to go with the factory set up. The Feds keep messin' with the manufacturers on what pads need to be made out of. Remember the asbestos issue years ago? So, factories change the pads to meet the regulations and then they must come up with a rotor that matches compatibility with the new pads. It is a vicious cycle. The aftermarket pads will FIT, but the composition is usually not right for the rotors.
Second, make sure whoever does your brakes uses the correct torque when re-installing the wheels. If you have 2 lugs at 70 lb/ft and 1 at 60 lb/ft, and 2 more at 85 lb/ft, you get uneven pressure on the rotor and after several heating cycles, the rotor wants to match the pressure of the wheel lugs.
Third, the calipers might be sticking, generating too much heat. I don't feel like this is causing your issues because when that is happening, you will usually see the pads wear out VERY quickly. Just a few ideas. Hope they help ya out....
