“generator”
Many Floridians in my hurricane-hit area had trouble with starting their generators because of old gas.
I got my older lawnmower to run reliably by drying out its gas tank using paper towels before adding new fuel.
Ethanol-free gas stores longer. It is available also in sealed gallon cans and will keep for a very long time (years).
Also, additives like Seafoam and Stabil will lengthen in-tank fuel life. Gas or diesel.
And remember, water will sit on the bottom of the tank and can be easily removed with a transfer pump.