So yes I choose to do what the manufacture says to do and get the metal and crud out of it??
Therein lies the problem. Some owners manuals say to change but the Service manual and my dealer say wait till 400 hours.
That's why I say if it feels good do it.
Those are termed "recreational fluid changes" It's a "manly past time", that is 99% feel good.
The log splitter in the shed has a "pressure drop" guage (so does the Hurlimann) that is placed in circuit to provide information to COMBAT the wasteful fluid changes that come from the "feel good psyche".
I do endorse clean fluids. but based on causality, not on emotion.
Take care of your equipment, but be aware of the facts. (send a sample out for analysis for example) Place a magnet somewhere in the sump!
Would you not expect the fluid filter to do it's job? That is my first line of prevention!
As a note, automotive automatic transmissions sometimes carry "lifetime" fluids. Though the transmission makers, like ZF, will tell you 30,000 miles is quite enough between changes. Let's do the math. 30,000 miles at average of 30 mph..(typical automotive use) that is 1000 hours! And an auto box is not so much different than a hydrostatic drive.
Just a perspective, I'm not trying to change anyones ways of doing things.