Back end oil on light use tractor

[Boomerang]

How often would you change the back end oil on a 20 year old tractor that does only 150 hrs a year, book says every 1200 hours or 2 years.
Spools are used only on Plough in autumn no trailers. I'm inclined to leave oil but change filters every 3 or 4 years. Thoughts please.

 

[Cowabunga]

How often would you change the back end oil on a 20 year old tractor that does only 150 hrs a year, book says every 1200 hours or 2 years.
Spools are used only on Plough in autumn no trailers. I'm inclined to leave oil but change filters every 3 or 4 years. Thoughts please.

Every eight to ten years, unless it gets grossly contaminated by water or something. I changed my Same's back end oil and filters a couple of years ago. Although I might change the filters again in a couple of year's time, I'm probably never ever going to change the oil again unless the transmission requires a repair. Its 25 years old and only does some 200 hours a year at most, like yours. It has some 6500 hours on the clock.