If it were new to me, I'd do the first oil change in the fall (my tractors so no winter use).
After that go by hours.
If you still want to change oil every fall with low hours, I would remove and drain the filter, and reinstall at the oil change. I would change filter by hours.
If you change the hydraulic fluid, there is a sump screen that should be cleaned. If your shift boots are torn, this is an entry point for water in the hydraulic system.
If your draft shaft (lower 3pt arms attach to) seals are leaking, ideal time to replace is when hydraulic fluid is drained.