Im pretty sure if you do the toothpaste, or any polish, on a semi regular basis, it will work fine to maintain clarity. In this case, years of neglect were too much for just the polish to overcome. I tried out the polish before sanding, and while it made a little difference, it wasnt enough. Sanding is probably required to "bring them back from the dead", using the polish semi regularly is the key to keep them from ever getting that bad again.