How late is "too late" to take protein at night?

Casein protein or at least a glass of milk at night (or right before you go to bed) helps with muscle recovery if you are lifting heavy. Makes a huge difference if you are doing a program like Stronglifts. I've found it's more the type of protein than the timing in terms of muscle recovery while sleeping. Casein protein is slower to absorb than whey and soy, and it allows the body to keep rebuilding the muscle over night/sleep time. For whey protein, GNC isn't that bad of a place to go as long as you don't listen to a thing they tell you! If you can, get a combination protein with both whey and casein and use it after your workouts and then either just casein protein or milk at bed time and you will hurt less. Made all the difference in the world. Since I moved over to using different proteins for different purposes, I've hardly ever been sore and I have been seeing HUGE improvement in the weight room too.

Experiment with timing. What works for one person may not work best for another. If you're still super sore on one schedule, try a different time!