So, the real answer? For a standard unopened carton, think of it like a snowman: it’s beautiful for about two weeks, then it starts looking sketchy. Trust your nose. Trust your eyes. Do not trust your hope that "it’s probably fine."
And here’s a pro tip I wish someone had told me: freeze it. Yes, you can freeze unopened eggnog right in the carton (just leave a little headspace for expansion, or pour it into a freezer-safe container). It will last up to 6 months in the freezer. Thaw it in the fridge, give it a good shake, and you’ve got a taste of Christmas on a random Tuesday in June. Now that’s what I call holiday magic without the guilt.
