2 Things:
1 - Today's motor oil doesn't break down with age under use as legacy motor oil blends did
2 - We put essentially that same oil in our vehicles and drive 3,000 or 7,000 miles, sometimes under heavy loads. Any residential mover would need to be used for decades to get that same level of use.
I check my mower oil level several times a year and change it about every 5 years. I have a snowblower that hasn't had an oil change in 15 years. I use it a handful of times a winter (maybe) and when I put it away the oil still looks fresh.