I shop at as many places as needed to get what I want at the best price, quality, and delivery terms.
I can't remember ever "quitting" a vendor - although I did a local barber here and that felt good.
Back when I was rebuilding my boat trailer I needed a few pieces of steel - guess where I ended up getting them? Yup - Amazon.
But not mentioned yet is eBay. I use eBay all the time or at least check with them before ordering anything from Amazon or locals.
I just replaced headlight wipers for the Volvo and a rear tail light on the Silverado and got a better buy from eBay. Pretty fast delivery too - just a few days....