Warped rotors are not uncommon. Be anal about wheel lug torque. Torque in a star-pattern in stages. First to 50 ft/lbs, then 75, then 100. Make sure the mating surfaces of the hub/rotor are clean, as well as the rotor/wheel. Clean the threads of the lug studs, and the threads of the lugs, then apply a small drop or two of oil to the threads to insure even torque.
Drilled rotors are a very bad idea. They may actuall cause warping, they decrease braking surface area, and are typically not for a street application. Micro-cracks can cause rotors to shatter. The only 'safe' drilled rotors have the holes pre-cast into the blanks, not drilled or machined. If they're drilled, they need to be properly stress-relieved before final hardening. And after all this, the rotor diameter must be increased to make up for the loss of braking surface area the collective holes create.
Buy quality rotors that are flat surface or slotted. After warping, turning may buy you time as you found, but they will warp again. Once warped, it'* inevitable.
Pay particularly close attention to your rear brakes. If they're weak, they put too much of the braking load on the front, causing excessive heat buildup.