If you read my posts you'll see that I said annual changes of oil are overkill especially when hours are no where near what would require a change dictated by mfg suggestions of hrs before changes.
I didn't say to never change the oils. If mfg states 200 hrs, I'll change when convenient for me after I hit 200 hrs, that maybe 220 hrs, I'll loose no sleep over it.
I pointed out that there are many that go way over on suggested hours and the equipment still runs and works. Point being that your tractor will not suddenly explode if you run over on hours.
As far as others tossing out whether we are talking hydro or engine oil, to me it doesn't matter. If the JD is telling you to change either on an annual basis when you are nowhere near the mfg suggested hours it is a waste of time and money.
Neither go bad sitting unused in an engine/gear box.