only thing I can think of that is not really touched on above is parking with the rotors hot. the space under the pad stays hot longer and can warp rotors. but it take a good amount of heat to accomplish this. just a thought. I would lean towards somthing like a slightly bent caliper mount or wheel bearing etc.any small problem in those areas could be the culprit. I am very hard on my breaks and so far aside from eating pad sets for supper I have had no problems, and I routinely see the glow on the curb from the drivers seat. I just changed my rotors for the first time, I went with brembo drilled/slotted to help stave off the fade that hard breaking down 100mph will cause. I have to assume that your breaking style must be much easier on this equipment than mine, which is why i think it is in the alignment of the rotor.
its all coming together, after a year.