I don't have natural gas at the house so rely on liquid fuels.
My choices are diesel and gasoline.
I have a 6000 watt diesel generator and use fuel from my RV to run it. The RV always has about 120 gallons of diesel in it, which can run my generator about 10 days of constant operation.
I also have a 4500 watt gasoline generator and use fuel from six 5-gallon plastic tanks I keep on hand. This can run the generator about 2.5 days of constant operation.
I always change out the fuel at least once a year. The diesel is used up in the RV and thus kept fresh that way. The gasoline is used in the lawn mowers, and all surplus over a year old is put into the automobiles and then replenished.
In the unlikely event I know the need for these generators will be longer, I would run the generators only a few hours a day for the refrigerators and freezers, and I would power the television and satellite receiver for the rest of the time with batteries and inverter. This would probably get me by several weeks to a month. By then, I would be out of food and everything else, and it would be time to move on to the bunkers.