Flaky pastry layered with butter, croissants typically don't need storage for too long because they're hard to avoid eating. But if you're lucky enough to have a batch, whether commercial or homemade, storage times are similar to any baked goods, with some exceptions for certain types, such as commercial croissants with added preservatives and croissants with fillings.
Storage at Room Temperature
Homemade or bakery croissants stay fresh at room temperature for about two days. Keep them from both drying out and absorbing moisture from the air by storing them in a plastic bag or wrapping them in foil. To bring the exterior back to a crispy, just-baked texture, heat the rolls directly on an oven rack at 200 degrees Fahrenheit, but leave them in for only 2 to 3 minutes so they don't get overly browned.
When you store croissants in the refrigerator, you extend their shelf life to five to seven days. Wrap the rolls in the same way you would for storage at room temperature, in plastic or foil. Croissants return to room temperature after about one hour out of the refrigerator. If you want to speed up the process, place the cold rolls directly in a warm oven for 3 minutes to heat them and restore their crispness.
Frozen croissants are safe to eat after freezing for one year, but they stay fresher if you use them within two months. Double-wrap the rolls tightly, first with plastic and then with foil. If you plan to cook unbaked croissants within a week, you can also freeze them directly on a baking sheet and place them directly into the oven without thawing. Baked croissants reheat well in the oven when they are still frozen; give them a few more minutes than you would heating thawed croissants.
Croissants with perishable fillings of ham and cheese, spinach or almond marzipan paste need to stay in the refrigerator or freezer, because bacteria could grow to unsafe levels within two hours if they're left at room temperature. Commercial croissants commonly contain preservatives that keep them fresh. Packaged croissants last a few extra days longer than homemade or bakery versions -- up to four days at room temperature and 10 days in the refrigerator.