The overall digestion is slowed.. so just putting in more of the whey/casein blend doesn't really achieve anything except, as you say, you waste protein.
If you've no other option go for it by all means; another option is egg whites pwo. Pwo makes a huge difference in my opinion, the quality and quantity of protein in that window of opportunity is extremely important to making serious gains.
For example, if you're not gaining, double your pwo protein - you'll see the difference (provided the rest of the diet is in check). Therefore, the important of pwo nutrition can't be stressed enough. It's the one thing I'd never skimp on.
Casein is fine any time of day you don't need fast-acting protein. It's mostly taken at night but I have it for breakfast too. (the same effect as casein can be achieved with regular whey with added milk or flax/olive oil if you go for pure whey)