I've never understood these questions.
They are like the "if you could only eat one vegetable..." questions.
Eat as much cottage cheese as suits your goal. If you can eat a gallon and stay lean and gain muscle, then that is the answer. If you can eat 1 tbsp. and you bloat like crazy, then the answer is probably 0.
The only problems you are going to run into, are high amounts of lactose, which most "physique" minded lifters tend to stay away from in higher amounts. For me, I can do a cup of yogurt, or cottage cheese, and be fine. If I venture into the 2 cup territory for too long, I tend to hold extra water weight.