I've never paid any attention to what goes in the gas cans, and hence, what goes in the gas tank for the generator. I put some gas in there a couple-three years ago and added some Stabil. I don't use the generator any to speak of so that gas is still in there. The generator always starts on demand, which might be three or four times a year. I do drain the float bowl at the end of the season before the trailer goes into storage. It's only 6 years old so we'll see how it goes.
This is a built-in Onan 5500.