How often do you change your differential oil?

When I bought my 2003 Kountry Star I immediately changed all fluids to full synthetic, engine oil every 5K real differential at 2K now have 118,775 on coach and have never changed out the rear again. Of all vehicles that I have owned I never change out rear fluid except to synthetic to replace dino gear oil, I am 70 years old and have never had a differential service problem NEVER. Do as you will, that's my story.