I freeze quarts and half gallons. They preserve seemingly indefinitely when frozen and the jugs hold up fine. Give it ample time to thaw before you use the milk, and it'll be normal. In a single person household without much home food prep this prevents a lot of waste without excessive trips to the store. As an aside, the stuff that comes from a partially thawed jug is interesting. It seems concentrated, as if the full water content is the last part to return to the liquid.