I've bought about five bottles now. I've never used the same toothpaste for so long, so I'm personally surprised. I used this as a temporary solution after having my teeth whitened once, rather than to whiten them, but I can't stop using it because it seems to keep my teeth white, even when I eat or drink foods with strong coloring agents. It's also easy to use, so I'd like to try the Royal version, which is only available online, and then consider using it again in the future!