Anytime I see milk on sale I always stock up, I live in the country and running out of milk is not an option. Yes I keep powdered milk on hand, but I prefer whole milk. Rarely will we go though more then one gallon in a week, but it depends what's going on in my kitchen.
If I'm making yogurt that week, or ice cream in the summer, we will often go through two gallons. But for those weeks we don't, I don't want my extra gallon to spoil. So I freeze it!
When I bring the milk home from the store I just pour out a little from the jug and put it in the freezer. This is important or else you may find your jug has busted once frozen. You then thaw in the fridge for about 2-3 days, yes this does require planning ahead. So take the frozen milk out as soon as you see your under a half gallon in the fridge. You can also freeze smaller portions in zip lock bags or glass jars so that it doesn't take too long to thaw.
EDIT- To answer some questions, no it doesn't change the consistency of the milk, however the milk does separate. So give it a good shake once thawed and you ll be good to go. Otherwise I find little to no difference in the taste and look of previously frozen milk.
Freezing milk Works for Me!