Right or wrong,  I go 2 years on smaller tractors.

JD3010 gets roughly 85-95 hours per year.

JD4020 gets roughly 120-125 hours per year

IH1066 gets only 60-70 hours, anymore. It might see 3 year interval.

Two main tractors (4440 and 8410) will get oil change every year, regardless of hours. (usually 180-215 hours each)