What pads is he using? Also is he using steel braided brake lines? The lines will increase the friction put on the rotors due to it allowing more pressure to be put to the caliper vs flexing the OEM lines.

Also, does he run the car really hard to park it with the E-Brake on? This will allow the rotors to cool at different times and in different spots which allows the rotor to warp as well.

Hope this helps

Kris