http://www.priproducts.com/research_technology_consumer.cfm
I have NOT read all these references, but I will say, using their gas treatment, in a farm bulk tank, right at four year old fuel was still quite usable. Ran it in vehicles, my wheelhorse, another rider mower, push mower, small home owner sized chipper, etc. This was , IIRC, 87 octane, non ethanol.
The owner got it for me to use with my duties, plus handed me the Pri-G. This was for work where we were caretakers to get to park my RV and have some place to live. The owner owned numerous very large truck stops, was in the fuel business as a retailer, this was their country retreat estate. He said, his research, this was the best you could get at the time. His nickle, I used the fuel, it stayed good for that length of time as I gradually burned it down and used it up. Steel bulk tank, set back in the trees a little in full shade, fuel delivered by the tanker truck. FWIW, YMMV.
Also had a large diesel bulk tank for the emergency back up generator, same deal, it was filled once, treated with Pri-D, I regularly once a month over that same time frame "exercised" the four cylinder diesel generator with that fuel, was still starting and running fine.