Yeah, if you don't ride the brakes, wait until the last second to stop and pull trailers with brakes..... it's not unheard of to get any of those mileages. I've seen it.
When I sold my Dodge diesel it had over 500,000 miles. I bought it with 250,000 on it. I think I only put 2 sets of front brakes on. I know I only did the rears once. But it had really big rear brakes.