How long can you leave sake out after opening (read text)

So everywhere that I’ve read online says that you should refrigerate sake immediately upon opening and that you should consume it within a week. But I’ve been to Japan before, and if you go to an izakaya, you can buy a big-ass bottle of sake and essentially open a “tab” of sorts. They’ll place your name on the bottle, and any time you come with your coworkers after work, they’ll pull the unrefrigerated bottle off the shelf and serve you. But the thing is, sometimes they’ll leave that bottle on the shelf for weeks or even months. So does sake really go bad after a week or two unrefrigerated?