May be a difficult one to answer but here goes, My 2012 350 diesel just turned 80,000 km. Out of this I think about 40k was towing a 8k fiver for three years and this year a 15 k toyhauler. Thinking ...
If calipers are working okay, Hawk Pads as mentioned already and vented/slotted rotors. If you plan on keeping truck and drive it during the winter, salt and crud takes it's toll, so tho you've gotten 80km on orig(?) equip, piece of mind, replace all 4 corners.