Since the results vary from patient to patient there is no firm answer. We do know that teeth tend to become darker as time passes, so touch-up treatments are occasionally needed to keep the teeth lightened. Your eating, drinking, smoking and home care habits definitely have an effect on how long the treatment lasts. Remember that the base shade of teeth is yellow or white and that we cannot whiten this base color. However, most patients are very satisfied with the results of whitening treatments.