Breast milk contains antibodies and important nutrients that enhance immunity, which can promote the baby‘s cognitive and physical development. Even if you only breastfeed, many moms find it necessary to pump and store breast milk at certain times for later feeding. According to La Leche League, breast milk stored in bottles at room temperature (66 to 78 degrees Fahrenheit) can be kept fresh for up to 4 hours and can be used for up to 6 hours. Refrigerated breast milk can keep 72 hours fresh, but can be used for up to 8 days. Frozen breast milk can be kept fresh for six months, and 12 can be used. If you are not sure about freshness, you can use some simple tests to determine whether breast milk has expired.