Yearly regardless and not with the cheap aftermarket Chinese crap cartridges, every 2 years air governor, purge valve kit with heater element kit. Yes maybe a bit excessive but I never pay billy bobs road service a #### ton $ for a service call. Proactive maintenance beats reactive maintenance
I agree with it. I spent $110 for a new cartridge and a Bendix governor. I just put on the cartridge. The current governor is 5 months old. So the Bendix is in the side box.