Does purified brand completely clean 7 day cleansing program clean you out for good?

They claim that this detox system cleans you out for good. I talked to the clerk at a local head shop about this product, and he said that some of the drinks sold at fitness stores such as GNC only cover up whatever it is that you are hiding in your blood, and only for a window of so many hours. I was told that the 7-day completely clean is supposed to clean you out for good, until you partake in certain activities again, say after your next drug test.