Warped front brake rotors 1997 Ford Expedition

I have a 1997 Ford Epedtion 2WD 4.6. I have had a problem with of the front rotors warping durning a long trip. It does not happen with town driving. I have had the rotors turn 3 times and the dealer says there is no problem. I am easy on the brakes and do not ride them. Is there after market rotors and pads that might help this problem? I would appreciate any input. Sounds like the rotors are too thin. You can really only get one or two cuts out of a rotor before it is below minimum specs. They warp more easily due to being too thin after about the second cutting. Raybestos makes a good aftermarket rotor, so does Wagner.....and the OEM FORD ones are good too.Car Repair Talk's forum.