Should the be changed every season ? Or every few years ? I noticed a fellow boater CK his with a Boris M meter, tapping the valve and looking at the meter. Thanks Tim Kish for that one.
I change mine every year, they seem to get hard after a season.
I also hook up my flow meter and wiggle the needle, if the flow jumps around more than just a bit I replace the o-rings, if it still does it it's time for a new unit.
Seems the brass hole where the SS needle seats gets beat out from vibration, usually takes a couple years...