Blue Ox recommends the tow bar be inspected and serviced every 10,000 miles. They charge $30 to do the job where they attend large RV shows.
I've had mine for about 23,000 miles now. I had it serviced last year at the Phoenix Good Sam Rally, before our trip to Alaska and the Northwest Territories and we'll have it done again in January at the Quartzsite show in preparation for next summer's 12,000 mile cross-Canada trip.
My neighbor had his serviced at the Pomona FMCA show last march and they showed him how it had lots of slop in the arm bushings and recommended that it be replaced. They offered him a 40% discount on a new one.
Retired and livin' the RV dream!
2005 Newmar 43 ft. MADP, Cummins ISL 400HP, 2008 Honda CR-V toad