> here in Canada it can last a month.

This seems to depend on the container as well as the brand / market segment.

"low end" Nielson / Sealtest / Beatrice in bags seems to last < 2 weeks, whereas stuff like Natrel / Lactantia / Nielson Truetaste in cartons seems to last around a month.

A month??? That’s definitely different.

UHT can easily last longer, it's shelf-stable (like literally on the shelf, no refrigeration needed) for months.

It's kinda wild it has as small of an impact on taste as it does. There's absolutely a difference, but it's surprisingly decent.

Oh, yeah, UHT can last for ages on the shelf. But I read it as referring to ordinary milk, in the refrigerator. "When I lived in the UK a pint of milk would last a week or so at most" sounds about right for that.

I personally think there's a big difference in taste, and I don't use UHT unless I really need to, but I'm sure that's partly just snobbery. You're right that it's perfectly OK for most purposes.