It takes time for a 2-litre container of frozen-solid milk to thaw. Even in the fridge milk only keeps so long. And the fridge in my old suite was horribly temperamental and delighted in randomly choosing which side of which shelf was going to be frozen solid, and when. I've had frozen milk, frozen egg salad (absolutely not edible when thawed; it's disgusting)... The only time I ever deliberately froze milk was when I had a small bottle of flavored milk. Stick it in the freezer, and when you want it, let it thaw a bit and then shake it up. It's like a milk version of a Slurpee.