Unlike most here, I'm a big proponent of replacing most failure items before they break.
Growing up, my Dad had a general aviation, sport aviation and racing aircraft engine shop. Parts were replaced and engines rebuilt on hours accumulated, not on failure. Too many opportunities to die waiting to replace a part until it breaks.
My entire career has been as a military aviator. Again, in military aviation, maintenance/replacement is done mostly on hours accumulated. Things break enough under a conservative system as this without running components to failure.
Do you sometimes feel a pinch in your wallet when you replace something that "appears" to still be good? Yup. Does it suck twice as hard to be sitting on the side of the road with a dead car, or having something break that causes engine failure? Double yup.
Water pumps, AOS, and things that have to come out and go back in while you're replacing something else all make sense to me to put on a regular replacement schedule.
Just my 2 cents worth and unasked for opinion...
