Freshly expressed human milk can be stored at room temperature for four hours and up to eight hours under very clean conditions, for four days in the refrigerator and up to eight days under very clean conditions, for 6 months in freezer and up to 12 months in deep freezer. Thawed expressed human milk can be stored up to two hours at room temperature, up to 24 hours in refrigerator, and it should never be refrozen. Leftover human milk should be used within 2 hours after the infant last finished feeding.
Here is a handy infographic to reference : LTLS Milk Storage
You can view the full ABM storage protocols here.