Once you've opened a bottle of prosecco, its shelf life is more limited compared to an unopened bottle. The carbonation in prosecco causes it to lose its fizz over time, so it's best to consume it relatively soon after opening to enjoy it at its best quality.
Typically, you can keep opened prosecco in the refrigerator for about 3 to 5 days. During this time, the prosecco will start to lose its effervescence, and the flavor may not be as vibrant as when it was first opened. To help extend its freshness, you can use a wine stopper or a sparkling wine closure designed to keep the carbonation from escaping.
It's worth noting that the exact duration of freshness can vary depending on the specific prosecco, storage conditions, and how well the bottle is resealed after opening. If you want to enjoy the prosecco's bubbles and flavor at their peak, it's best to consume it within the first couple of days after opening. If you're unable to finish the bottle within that time frame, consider using the remaining prosecco for cocktails or recipes that call for sparkling wine.