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 ...
My 12 only has 50k on it but I changed the front and rear on my 05 at 80k. The old ones were not gone but the squeak drove me crazy. I replaced them with Hawk Performance pads and it made a huge difference in stopping power. Now it stops better than the dually.