If you believe in following manufacturer's recommendations, even partially, the generator needs to be run periodically under load. Onan suggests 2 hours per month under some load. We use our generator when we are staying overnight anywhere we aren't on short power (DW uses O2 concentrator at night) and to run the roof AC's while traveling if it is very hot. So, we depend on it and it gets a monthly exercise. IMHO, if you are only running it couple of hours per year, you are asking for problems.
I am a firm believer that mechanical things will let you down when you most need them if you don't take care of them.