I replaced the front pads on my 10 GT at about 65K, but I did not own it for the first 36K miles. Never touched the rears as they were still good. The guys at the Firestone let me know the front pads were almost gone when they rotated my tires. It was a very easy brake job.
If the fronts look OK, it is possible they were replaced, and that the rears were not. Rear disc are a bit more involved as you usually have to twist the piston to make it retract. I now have the piston tool kit I got for 50% off,
http://www.harborfreight.com/disc-brake ... 61381.html" onclick="window.open(this.href);return false; but I used to "rent" it from Autozone. I haven't worked on any rear disc except for my Mustang and our old Yukon, but they were not too hard to change.