What to know before serving an old bottle that could fall a little flat.

There are occasions when nothing but a little bubbly will do. The problem? We may not always be as prepared for them as we would like. Maybe we've forgotten a loved one's big birthday, didn't realize our special someone would get promoted, or didn't expect a couple's spur of the moment engagement. Unless you've got a fully stocked, expertly curated and moderated wine cellar, unexpected surprises like these may lead to panicked searches for a bottle of Champagne or sparkling wine.

So let's say you luck out and find an unopened bottle, but you're having trouble remembering when you received it. Depending on how old your bottle of bubbles is and how you've been storing it, it may be fine. But then again, it may not be quite so nice. Before you get down to the business of uncorking, it's important to consider some key information. 

How Long Does a Refrigerated, Open Bottle of Champagne Last?

The short answer: not long. Just like a soda or sparkling water, the longer an open bottle of Champagne or sparkling wine sits, the quicker you're going to lose carbonation. There are lots of effective stoppers that can help slow down the oxidation, but as a rule, you should stop it up, refrigerate it, and then try to drink whatever is left in an open bottle in one to two days. (But honestly, only serve an already-open bottle of wine to your celebrant as a last resort.)

How Long Does Unopened Champagne Last?

In order to figure out how long your bottle of sparkles is acceptable to serve, you're going to need to look at the label. If you see a year, it is a "vintage" bottle, meaning your Champagne or sparkling wine was made with grapes exclusively from that particular year's harvest. If you don't see a year, it means it was made with a blend of grapes from different years.

As you might expect, the "vintage" bottle is going to last longer—up to 15 years if stored properly. A "non-vintage" Champagne may only last about 3 to 4 years. Of course, there are exceptions to these rules—some Champagnes and wines are just not very good from the get-go. But what's the proper way to store unopened bottles, you ask? Ideally, if you can find a spot that is dark, cool (50 degrees or so), humid, and allows you to lie the bottles horizontally (it might be worth investing in a rack, that's going to keep your Champagne in good condition. Just do the best you can.

WATCH: Blushing Mimosas for Any Time of Day

How Do I Know If the Champagne Has Gone Bad?

If your bubbly has no bubbles, it's probably past its prime. And if you notice the color has gone a little too golden or smells sad and sour, it's likely not at its peak. The good news? All of this is very subjective. What's "bad" to some is tasty to others. The better news? You won't get sick sipping a "bad" Champagne. The worst that can happen here is that you may add a little sourness to an otherwise sweet toast!