I was stopping at two different supermarkets for my main grocery list, but I still needed to stop at several specialty markets for some of my ingredients. I still stop at the specialty markets, but I’m down to only one supermarket, Whole Foods. I had to give up some brands that I would get from the other supermarket, and that was the only reason I would stop at two.
My wife does our regular shopping at one store, mainly because she works there and gets a discount. The only thing we fight about from time to time is when she stocks up on the "store brand" items because she gets an additional discount on those.
With certain things I can taste the difference in say something like their chili powder when compared to McCormick's chili powder. So, I insist on brand names for quite a few things.