If you ask this question in a google search, the likely answer will be 3-5 days. However, that is not our opinion at all! Seafood should always be consumed fresh and served on the day of purchase or the next day. Store in the net and paper bag packaging from the store or in an open container such as a bowl with a dampened cloth laid loosely over. They do need to breathe and should not be submerged in water or wrapped in a plastic bag while stored in the refrigerator. When buying mussels (unless you’re deep diving for them yourself, that is!) it's important to check that they are stored properly at the market, preferably on ice or in a cold wet environment.