Whenever you find a good deal, you can take advantage of it by freezing the milk for long term storage. This can allow you to store up to 6 months of milk if you are blessed with the storage space.
Count how many days from the current date to the expiration date. This is how long the milk will be good for after thawing and needs to be written down to help you keep track.
If you find that your family can go through a full gallon in as many days as you will have after thawing you can stick the jug right into the freezer as is.
Milk can be kept for up to 6 months in a freezer. Write the number of days the milk is good for directly on each package before freezing.