I have noticed that one CD (part A or B) works great the first few days and then either the brain gets used to it, or the effect is not there any more.
That's one of the reasons that it's recommended to get feedback from others. You only notice when you make the initial movement, then you kind of get used to it, so you don't notice any more.
I've noticed that myself with paraliminals, and EFT, and other stuff. The effect is there all right, it's just that's it's become "normal" so you don't realize it.
Kind of like when you go on a diet, you might notice the first couple days, but then exercising and working out is normal. Then your friend sees you for the first time in a couple months and says:
"whoaaaa!"