I'm at 55000 still have 7mm left on pads front and back, and all wear is even. I'm a minimalist braker, I can make brakes go a long time.
Theoretically you shouldn't ever need to replace rotors unless something went wrong, i.e. caliper isn't releasing all the way because guide pins are sticking causing improper wear; bad material in pads, other debris getting on the rotors causing them to grove...and of course, regular overheating of brakes caused by extreme braking either as a bad driver, or just extreme conditions, or racing.
Many people say it's not a good idea to turn rotors, I say as long as they are not grooved or warped, a thin resurface with your first set of brake pads replacement is fine. Again, any grooving or warping, it's not worth the hassle of "trying" to salvage them with excessive resurfacing.