Once your teeth are whitened, you’ll need to whiten them every 6 months or once a year to keep them looking the way you want.
Even after a professional whitening, your teeth can still get stained from outside from drinking colored drinks like coffee, tea, red wine, and from smoking. Rinse your mouth with water after a dark drink to lower the chances of stains. You can also pass a damp toothbrush over your teeth and give up smoking.
Excessive bleaching is not advised that can damage your enamel, whiteness of teeth lighter than white of your eye will not look natural.
Any teeth whitening procedure cannot give you permanent results however results can be prolonged by taking good care of your oral hygiene and limiting consumption of tea, coffee or any other incriminating food.