I had a customer who had 5 or 6 Crew Cab Ford duallies /99-03. They were 2 wd 7.3 XLT Lariats. They had camper shells and hauled 2500 to 3500 pounds of electrical components, most of the time they hauled 4 grown men. Every 35,000 to 50,000 we had to replace pads front and rear and replaced the front rotors due to small cracks all the way around, we tried to turn the very first pair but experienced fretting over the cracks. All the trucks received at least 1 new engine between 200,000 and 300,000 miles.
@sugarray, if you got 52,000 out of the original pads I would drive it anther 10,000 miles and replace front and rear pads only if you have no shimmy or funny noises. Brake wear is relative to driver style and amount of load that is being stopped.