Intrusion.
Clinton,
"Only the right maintenance, carried out in the right way at the right time, means more safety."
Encapsulates the belief of many an ame, but maybe look at this way, as you mentioned, a Vac Pump left alone, can often operate quite safely for many years
And hours without failure, and without replacing it at that 500hr mark you do avoid introducing human error and intrusion into the equation.
But, as has been proven many times, allowing aircraft to be maintained with loose component overhaul time frames in many cases leads to components operating long after they should have been removed and overhauled/replaced,
For the same reason as you suggest some components are renewed-maybe prematurely,
"continue the religious metaphor, merely faith-based maintenance that often turns out to be counter-productive"
This works both ways, some people leave components far longer than designed, in the belief that it will never be a problem or fail, rather than change.
Surely you can see that by enforcing component manufacturers recommendations for component overhaul periods, removes the opinion of the maintainer out of the equation, and also places liability back onto the component
Manufacturer rather the ame.
I've seen a few cables break at the swage fitting, held together with the lock wire, the cables were not worn and looked fine, not corroded, but broken they were. Had they been on a regular replacement schedule-maybe 15yrs, that would probably never have happened, but yes, in changing them, again, you introduce human factors-error and intrusion, but they won't last forever.
I couldn't agree more about the right maintenance at the right time, but unless you can guarantee everyone maintaining those aircraft are singing from the same hym sheet, the only way to ensure things aren't let go until they break is to enforce the manufacturers time frames, take away the decision to do or not to do so to speak.
And the Data, why do you think hartzell 10yr period is enforced, and not (in some cases) McCauley. AD/prop/1
It's not that one is immune from corrosion ect, but not enough of the Data about what was found in the field made it back to the regulator. (My opinion)
But as you suggest, unless there is a big difference in failure rate seen between manufacturers, does it matter, probably you find out when eventually overhauling the McCauley and everything is thrown in the Bin..
Get used to the idea now of Sched. 5 gone. Except if you own a Cub..