We seem to have two subjects going here - I' d like to comment on ethanol problems...I don't have any.
I guess solvent/tank issues and hoses and gaskets that can't tolerate ethanol are real, but I've not had any problems with that. Nor have I had any problems with phase separation or old fuel. My experience otherwise has been that storage is not a problem if gas that evaporates from a float bowl is not allowed to be replaced. Turn off the gas valve so the float bowl is not an evaporation chamber for the entire tank.
Once 'gunk' forms in the carb, no amount of additives will help, it must be disassembled and cleaned, although draining the bowl and refilling it with carb cleaner via the drain port will help a marginal problem if allowed to saok long enough.
As for Honda generators - at least the "i" series...the storage recommendations are to completely dry the fuel system, but if the on/off switch is off and the vent on the tank is closed I don't have a problem because once the float bowl is dry, it stays that way. In working with three models of the "i" series, I have found that if the generator doesn't start on the first or second pull, no matter how long it's been inactive, a shot of fuel in the sparkplug hole will get it going.
So while the ethanol problems are real for some folks, it hasn't been the case with me. And as far as old fuel goes, I'd rather run it thru the Quadrajet on my 350 Chevy/Volvo than put it in my modern fuel injected vehicles.
Additives? I have a bottle of Pri-G which I seldom remember to use.
PRI Advanced Fuel Treatments
Oh, and pure gas is available around here at about every 10th station, but I can see no reason to pay a premium for it for use in either my (trailer) boat or cars.