Some facemasks can expire and have a best-before date. These face masks that might "expire" are the N95 filtering facepiece respirators. While they will have a date for use on them, they will still offer some protection even after they "expire" - but it will not be as effective. Therefore, it is so important for healthcare workers to be equipped with these specific masks.
Dr. John Balmes, professor of environmental health science at Berkeley Public Health recently told Business Insider that they do not expire in terms of their most basic function - to cover the wearer's face and mouth - but the specialised seal that this mask is known for can become worn. As a result, the masks will ‘expire’ and won’t offer the high-level protection that they are made for.
Cloth masks with removable filters should be replaced after extended wear. These filters will become less effective whenever you wash your mask. It doesn’t mean you should wash your mask less often, but it’s important to consider this and replace your mask reasonably often - once a month if possible. Keeping at least two masks on rotation can also help with extended the wear time of your face mask.