Based on my experience running all manner of clapped out junk with engines 2-3yr for an engine that sees dozens of operating hours per year and runs on propane/

Based on my experience running all manner of clapped out junk with engines 2-3yr for an engine that sees dozens of operating hours per year and runs on propane/natgas seems fine. You're not pampering it by any means but you're not neglecting it either. Engines running on gaseous fuels tend to have really clean oil. I'd be more concerned about things nesting in it than anything else.