I'm all for designing for walkability, but this is a case study in failing to understand audiences. If you make this not just a possibility but a requirement of walkable cities, many people won't want to live in your "walkable" cities at all.
There are much better arguments possible here. For instance, you could promote CSAs for regularly delivered farm-fresh produce, or establish efficient grocery delivery services that use one vehicle to deliver to many many customers, or other potential options that don't involve regular car trips for grocery shopping and don't involve spending an appreciable fraction of your day shopping.
if you're concerned about how your time is spent, i think you're missing a fundamental piece of the puzzle: how much time you spend driving. you could end up saving an enormous amount of time while still going out to shop more if you cut out driving and reduce the scope of your trips.
Nope, weekly trip to the store minimizes all of the issues.
Milk is not supposed to last for a month.
(For clarity in case there is a nomenclature difference here, UHT milk is shelf-stable liquid milk that's entirely equivalent to any milk but lasts much longer before expiring. That's separate from things like evaporated milk or powdered milk, which are also substitutes for milk but not directly equivalent.)
I once was at a farmers place - when they were done milking the cows in the morning they brought milk in from the tank for breakfast - ever since then I can't drink store bought milk as fresh milk tastes so much better. (the milk was also unpasteurized, I believe fresh was the key to taste but I'm not sure)
But in any case, it's good that multiple options exist.