Regularly used outdoor equipment, I change the oil every 50 hrs. or 4 years (snowblower and push mower), whichever comes first. Both my riding and push mower are over 20 years old. The push mower might be 30+ but gets far far fewer hours once I got the riding mower.
The snowblower in particular is picky about not being stored with gas in the carb, gums up easily. Zongshen SN210 engine, at least generic carbs are cheap on ebay but it takes a bit of effort to de-shroud the engine to get to it.