A friend of mine has a summer place on an island in the Great Lakes.
It is powered by a combination of deep cycle batteries and an Onan 4KY salvaged from a Class C m/h.
Last I spoke to him it was still going strong with MANY thousands of hours on it. It runs during peak demand hours and both powers the demands at hand and recharges the lead acid battery bank.
It also runs ONLY between Easter and (Canadian) Thanksgiving (2nd Monday in October) each year with no monthly ‘exercise’ in between and has flawlessly for several decades.
Several mobile mechanics and utility contractors around here have them on service trucks, they run them well over 10k hours.