My motorhome is an 04 with over 40k miles, and last time I had it at freightliner they told me I had 75% life left on the brake pads. I was there getting the right front pads replaced because there was seal leak and grease soaked into the pads so I had to get that leak fixed and they replaced those pads. I was going to have them all done since it was there but the guy said there was plenty of life left and said motorhome brake pads usually get over 100k miles. His reasoning was most people use the jake brake so they don't wear the pads as much. I do use my jake brake a lot, even on level ground.