What's shelf life?
Earlier this year, I drained 40 gallons of 20 year old gas from parts boat. Been mixing 50/50 With fresh. Running log splitter and mowers no problem.
Last year used 10+ yr old gas mixed 50/50 in 91 F350, ran fine.
Imho, old gas can be used, just have to get used to the varnish smell.
As to e10, old 60's Japanese carbs have rubber o rings that will harden and crack from alcohol.
Non of my Quarda jets care, but wouldn't want to put too much through my 85 Johnson VRO V6 or chainsaws even with the oil in the gas. Any older carbs with rubber parts should see as little alcohol as possible.