I've been using the Stabil 360 for 3 years. Like others, I add it to every 5 gallon containers when I fill it year round. I get it in quarts with the measuring tube on the bottle. 1 oz. treats 5 gallons/160 gallons in all. It stabilizes, and cleans, eliminating having to add Seafoam at the same time, with regular Stabil. I use it in anything from my 50's era vintage garden tractors, to up to my 65 hp farm tractors, and everything in between, except my newer Stihl saws, which I use Marine (no ethanol) gas in.
I also use battery maintainers w/desulfater on several pieces, from my backhoe, Dodge Cummins Dually I pull the horse trailers with, to my Super C Farmall which I leave on the manure spreader most of the year, and 4-wheeler that don't get used as often. Two of those are 6V/12V so as to use on my older tractors, so they are always ready to go when needed, especially through the winter. These range from the $40 Harbor Freight model, to a couple more expensive brands. The HF one is on it's 3rd year, hooked up all the time to my Super C, so I can check it twice daily while doing chores, and still works fine.