In Washington state, spring rains plus pollen is like moving elmers paste, so to ensure there are no streaks from winter blunders I change them out. Then I get a set for pushing off bug guts all summer long. Then a Final set goes on at Hunting season. I average 18-23k a year. So if I change one I change them all.Change blades 3 times a year?! Yet you say you pretty much don’t need to use wipers? Are they regularly (every weekend or more) wiping mud off or something??
Here I am being somewhat disappointed if my wipers don’t last more than a year.