I tend to say ,if you found them to work thats great, as you can see there are a lot of diffeerent products and its more about which one is right for each stain which is the tricky bit. I also say its important to flush the products out, do you have the correct appliance to do this, otherwise it is similer to shampooing your hair and leaving it on without rinsing, would you consider that to be a sensible way to clean your hair, and would you normally rinse with cold/boiling water, of course not! if they are not convinced I wish them happy cleaning and move on.. Simon