The storage time of milk after it is expressed is determined by the environment in which it is stored. If the milk is kept at room temperature, it is usually stored for two hours, after which it is not recommended to give it to the baby. If it is kept in the refrigerator for 24 hours, and in the freezer, it can be kept for three months. After you take the milk out of the refrigerator or freezer, you have to re-warm it before you can give it to your baby. You can put the milk in a milk storage bag and soak it in warm water at about 40 degrees, then give it to your baby after the milk is naturally rewarmed.