Maybe a different perspective from someone who has resuscitated many barn finds.... its quite amazing how the different systems work after all these years and what does/doesn't survive the ravages of time. Engine oil is obviously bad, when I remove the drain plug there is a lot of condensation that pours out first, coolant is surprisingly usually good, as long as a good mix was left in there, transmission fluid is always good even after an extended period especially considering the old systems were "open", brake fluid is garbage usually and takes out all the stuff with it (seals in master, calipers, wheel cylinders)...
A job not done is better that a job half done, if you plan to keep your vehicle for about 15 - 20 years, stick to the normal use case service intervals and you will help yourself dearly (and then discretion by testing on top of that on most things!) unless you are driving in a lot of dirt roads, extended idling in hot weather, towing, and hauling which is the classical definition of severe use.......
You are more likely to mess up something by getting stuff messed with by a “code reader” as I saw being described in a post yesterday. Maybe brake fluid because it’s a safety item, but even that not at the severe interval.
About the claim of severe use, I’d like to understand how short tripping can and affect anything except engine oil. Everything else is a closed system, and moisture is usually the aggressor in an open system. I can possibly see transmission fluid, but even that is closed unit these days.
Coolant is relatively easy to replace, but you can also test it before needing replacement just a simple multimeter for electrolysis, and also you can check mix with a cheap $5 hygrometer.
