I have had motorhomes off and (mostly) on for almost forty years now and have had an Onan problem one time. I forgot that they shut off if the gas level in the rv tank is about 1/4 or less full. About means about I found out.
Fortunately, I live in an area where I can store my C within a few miles of my home and our winters are a few days cold, a few days nice for the entire season. So, on a nice day around the first of the month every month I get it out of storage and drive up the highway about 30 miles with the generator running and under load. I stop, eat a burger for lunch in the little town up the road, drive back to the storage and another month's maintenance on the rv and generator is done. One sixty mile trip and a couple of hours time including a burger and fries is a small price to pay to keep my rig ready for travel season.
Of course, I change the generator oil, change or clean the filter and do all the other normal maintenance as required as well but I have concluded that exercising it is a cheap price to pay.