How do you ensure that the gasoline that you purchase is the best quality?

A little query seems to show that premium gasoline only makes up 11% of sales nationwide. I sometimes wonder if the particular station I buy from sells it routinely enough to keep their inventory “fresh”. Am I crazy or can you unknowingly procure vintage gasoline?
The internet has also lead me to believe that the bargain station that I may go to for my daily driver probably is not the place to take my old car. Do many of you seek out distributors of “Top Tier” fuels? Economy gas station brands don’t sell them apparently. One has to seek out stations that do.
I can’t say that I have noticed changes in performance regardless of where I bought the premium, or the rare times that I put regular through it for that matter. I think that the car did not like that one batch of non ethanol regular I bought once however. Should I pay more attention to the quality of my gasoline?
Thanks