If probably sealed it can last years, fact! I’ve used 2 year old e85 that was properly sealed and had zero issue. I even let my e85 in my tank sit for 6 months during winter and it is fine come spring time. I’ve cracked open my fuel filter to see nothing but a new clean filter. My pistons look great when I examined them with a boroscope. If you can burn through a tank every 6 months I don’t see why anyone wouldn’t do it. The pros FAR out way and minuscule cons imo.