My coach had 31K miles when we got it so I got the kit from NAPA for about $100. I had planned to change it myself but let my RV guy do it at the annual maintenance...he charged me one hour labor ($55) to do it. He told me (as did the local FL folks) that I could probably go 4 - 5 years if I was only going to put 5 -6K miles on it per year.
'07 Country Coach Allure 470 Siskiyou Summit #31578, Cummins ISL 425; 2014 Ford F150 toad; Air Force One Toad Brake.
Glen Allen, VA; Smith Mountain Lake, VA.