I would have to agree with Rusty. Not everyone puts 50K miles on their truck every year. We owned our '98 V-10 3500 4x4 for four years, and managed to accumulate a total of only 36,000 miles on it, of which 90% were accumulated while towing 9,000 to 11,000 lbs. We had no engine knock, no pinging, and no other problems what so ever. In four years that truck never needed a trip to the dealers sevice dept. , not even one single time. It was the most reliable vehicle I've EVER owned.
My '02 ETH/DEE 3500 4x4 has already been to the service dept. to try and figure out why it doesn't make the power that it should (I was told nothing was wrong with it).