I'm not entirely sure when I last bought a bottle of apple cider vinegar, but I'm certain it was a long time ago. And though I've definitely opened that bottle and used the apple cider vinegar a couple times, probably to make salad dressing or something, that bottle of apple cider vinegar—or ACV as some folks call it—has been sitting, mainly unused, on my pantry shelf. But that can't be the best way to store apple cider vinegar, can it? Does apple cider vinegar need to be refrigerated, or can I just keep it out in the open until I need it? I know you can use ACV in pickling liquids, but I don't think that means the shelf life of apple cider vinegar is endless, right?
Turns out that I've been doing it right the whole time without even knowing it! According to the Vinegar Institute, a trade association that represents vinegar manufacturers and bottlers around the world that is a real organization that actually exists, you do not need to pop that open bottle of ACV in the fridge. The acidity of vinegar means it's "self-preserving and does not need refrigeration," and theoretically, vinegar's shelf life is indefinite, even after you open the bottle. The manufacturers of Bragg's Apple Cider Vinegar just recommend that you store your ACV "out of direct sunlight in a relatively cool location," for best quality.
And really, the only thing that will be affected if you hang onto a bottle of vinegar for years is the color and clarity of the liquid. This is especially true of apple cider vinegar, which is functionally made from fermented apple juice. The changes don't necessarily affect the flavor of the vinegar, but it's almost certainly one of the reasons the US Department of Agriculture recommends that you use vinegar in your pantry within two years from date of purchase. The USDA also requires that bottles of ACV come marked with an expiration date, which is another good way of knowing when it's time to re-up on the good stuff.
If you do use a bottle of "expired" apple cider vinegar, don't panic. Bragg's Apple Cider Vinegar, for example, has a listed shelf life of five years, though the manufacturers note that, "due to its nature, Bragg ACV can be safely used for many years after the expiration date." So chances are good you'll be OK—but if you've had a bottle of apple cider vinegar for over five years, it might not be a bad idea to put ACV on your next grocery list anyway.