> Best is to have some type of long term storage like a Diesel generator
LNG or propane would be far superior fuel types for long term standby generators. Periodically exercising a machine that runs on CH4 results in very minimal buildup on internal components. Liquid fuels are much dirtier and can also go bad.
Diesel is used in situations where you can afford all of the crazy maintenance. It's worth the trade off if you can.
The maintenance difference isn't that large. Diesel in a good tank also lasts an extremely long time, unlike gasoline. Diesel engines are more thermally efficient so you get more electricity per unit of fuel burned. The tanks don't need to be under pressure or replaced nearly as often as those for propane either. This is why most hospitals, data centers etc. that aren't near a natural gas line use diesel generators not propane. Natural gas has the benefit that when piped in, you don't need storage at all.
If you have access to ethanol-free fuel, that basically eliminates gasoline "going bad". It's the ethanol that degenerates over time.
I wouldn't say it "eliminates" it. Even without ethanol, gasoline still goes bad far faster than diesel. Gasoline is full of aromatic hydrocarbons that eventually will break down, and after a few years you're left with a brown stinky liquid.
Up until a year ago where I live, Chevron 94 Octane was ethanol free. I had issues with older carbureted engines after leaving gas in them for ~2 years. With E10 I wouldn't dare go that long as it can be so corrosive.
I can fill diesel tanks myself if need be.
I'm going to have a hell of a time with LPG.
There are dual-fuel generators, Ecoflow has a propane+gasoline option [1]. The problem with a pure propane setup is that propane doesn't really want to get gaseous if it's too cold outside - just like your cigarette lighter that you need to warm in your pants pocket before it can actually light a fire.
Diesel plus <any other kind of fuel> isn't available on cheap residential units I'm aware of, particularly as the ignition and fuel injection mechanisms are much more complex than a gasoline/propane mechanism.
[1] https://www.ecoflow.com/us/dual-fuel-smart-generator