I purchase my fuel @ high volume stations, 35 to 50 gallons at a time.
I leave it in some equipment only used once a year and have never had a problem.
But after a year, I have found it goes skunky.
A fuel shut off will work well for anything less than a year, would be a good rule of thumb.
Around here RV gas goes near a dollar a gallon more, and they don't sell much of it.
I wouldn't venture to guess just how many months or longer it sits in the tanks before it is sold.
Just my findings your situations may be different.