Good question
I have a friend who has a 1998 4runner SR5. He believes he has over 80,000 miles on his pads. Of course, he doesn't work on his truck, and just pays the bills, so he might have had them replaced and not know it.
I had to have both my front rotors turned at 13,000 miles ( brake pedal pulsation ). Recently (14,200 miles) the left rear caliper started to make a tiny squeek during the final 20 feet of braking, at just the right pedal pressure.
I took the wheel off, pulled the caliper, and relubed the caliper sliders myself. Noise has been gone almost 600 miles now. Hope it stays away for good!!