Dude same here. Eventually you plateau, and pretty much devastate all of the time, and it's hardly a challenge. Once the challenge is gone, like anything, it gets suuuper repetitive, and loses its fun. Apparently I have ADD and the concept behind playing so much COD or video games hours on end is that you don't have to think. It's just one, particular, focused activity that blocks out everything else and all the other thoughts going on in my brain that runs a million miles an hour.