I check the run-out of the wheel bearings on my Dexter axles per Dexter's recommendation of every 12,000 miles. They are cartridge type bearings, like the wheel bearings on the front of a car. They have been perfect so far, but I'm afraid of them ever going out on the road. It's a real production to find a new bearing and a press is an absolute requirement to get the old bearing out of the hub and the new bearing back in. They are supposed to last a couple hundred thousand miles, but I stick with Dexter's suggested inspection schedule. I didn't know cartridge bearings are used in RVs. Have you had any experience with cartridge bearings? How long would you expect them to last? Do you think it would be prudent to proactively replace them at X miles?