They sell both 2-stroke and 4-stroke ethanol free engineered fuel at Home Depot and the like, I think the 4-stroke is gray. But it’s expensive af - currently $24 for 110oz which is like $28 per gallon
Where are you buying these valves? I've had a lot of shit go bad because of ethanol, but I don't think I've ever seen a fuel shut-off valve go.
The problem isn't seeing fuel for 9 months, it's when the machine sits too long with untreated E10 soaking up water, and then the water and alcohol form a gel that gaks up the works and exasperates the other long term storage problem, varnishing.
I recommend going to a landscape supply shop, or mower repair shop that stocks parts and get a better valve made of metal. You will also benefit from adding a fuel filter to catch crap before it gets to the valve and carb. It is a very easy mod