Basic article on long(er) term storing of Milk and Eggs
http://www.offthegridnews.com/off-grid-foods/the-secret-to-long-term-safe-storage-of-milk-and-eggs/Note that "long" term for milk is about a year and eggs about the same.
This is NOT dehydrated milk, it is frozen.
The use of freezing assumes that you have a means of keeping your freezer running. Unless you already have a working solar electric system, with adequate battery storage, this option is not viable.
Where it does work is to buy Milk and Eggs on sale (right... I haven't seen any lately, either) and be able to buy in quantity. This is a gamble and it can reduce your food budget, allowing you to buy other foods which really do allow long term storage.