On it's own, without any additives, most gasoline will last 90 days, depending on the weather. Gasoline is formulated for different regions and different times of the year, and so holding over winter gas into the summer may be problematic. One of the advantages of manufacturing gasoline as they do is the limited shelf life, preventing people from "hording" a cheap supply in anticipation of prices going up and/or supply becoming limited. Gasoline is a hodge-podge of distillates, quite volatile and subject to continuous chemical interaction. Each component also has a weak molecular bond, making it easily decomposible by heat, ionization, depressurization, contamination, etc.

Alcohol would be far better for storage, but internal combustion systems don't seem to like it so much.

Sooner or later, we are all going to need a Mr. Fusion converter.