I have found just the opposite around here, though maybe I just shop in the "right" stores. Since I live alone and do not drink milk, I use it primarily in cooking. A quart will go a long way for me, and I find, properly stored, it will keep over a month after the sell-by date before any curdling and/or sour taste or smell occurs.
I feel the key is "properly stored" (maybe your grocer and his help are not observing the basic rule of milk-product storage: The colder, the better, and never off refrigeration for even 5 minutes.)
If he is handling the milk properly, then maybe you are not after you buy it. Never store milk in a refrigerator door; store it as far to the rear of the refrigerator as you can. (Warming & cooling & warming & cooling each time you open the door spoils milk faster than anything.) Also, never let milk sit out on a counter; pour what you need and get it back under refrigeration immediately. Never pour milk or milk products into another serving container and later back into the original container. Never store milk or milk products in anything other than the original container. (No matter how many times you wash another container, it will never be as sterile as the original packaging.) If the temperature is above freezing outside, carry an iced cooler with you in your car to store your milk while you are driving home; carry a cooler with you if it is below freezing outside and you are going to be driving with your car heater at full blast. Always plan to do your milk buying at the last store you shop before going home.
By the way, I am not just pulling these thoughts out of my rear, as I was a Dairy Manager for 37 years for a local chain of grocery stores, until I retired.
Thanks for the tips. I do keep milk in the back of the refrigerator. The fact that sometimes it will last for more than a week without any problems (I do drink milk and my grandson guzzles it, so it is not a matter of needing it to last a long time) would seem to indicate that there’s nothing wrong with my method of storing it. I buy my milk, paying close attention to the sell-by dates, at my local Kroger, Giant Eagle and Meijer stores. When the milk goes bad prior to the sell-by dates it is an equal-opportunity problem in that it does not matter which store it came from.