Don't Freeze Milk
Although it's ok to freeze most foods under the right conditions, it doesn't work as well with milk. When you defrost it, you'll find it separates and becomes slightly chunky, and it's no longer the consistency you want for drinking. However, if you want to use it for baking, that should be fine, as you won't notice the consistency that much.
Look for Milk Alternatives
If you can substitute milk for cream, then buy that, as it will last longer. Or, you could try plant-based alternatives, which also last longer and have a similar nutritional profile to milk.