Well, Gentlemen, a fascinating range of answers.
The same scenario applies in the motor -Trade..... Rolls Royce (as was) scheduled an extremely short service life for hydraulic hoses (4 years)
and, from memory, there's 10 0r 12 on a Spirit! (suspension and brakes licensed from Citroen and using non-corrosive mineral oil)
So, when did you renew all flexy's on your Escort/toyota/whatever braking system? ( And they all use DOT 3/4/5 Brake fluid which is extremely hygroscopic and rusts the system from the inside )
I suspect that this is all about arse-covering...it has nowt to do with sensible service life but all about inducing paranoia in the user and generating a profit-stream for the equipment-maker..... of course Rolls breakdowns were rare...just about anything that was likely to age or wear was scheduled for a service-change with a reserve margin putting it in the Helicopter or space-shuttle league.
Instead of blindly following "'cos the schedule says so," could someone (other than those who say Common sense,- it isn't very common)
can we have a rational reason why a seal you replaced a couple of weeks ago, is suddenly no longer serviceable.....
do you suggest that if a maintenance -sequence involves, say, building-up, measuring,partial stripping, adjusting and reassembly.....you'd change ALL O-rings and seals EVERY time? that could entail a lot of "used" parts before the rebuild even got completed.
I am NOT advocating that manufacturer's schedules should be ignored, just curious about how many follow blindly and how many question the rationale.