The results from professional teeth whitening vary from person to person but can last up to 3 years. Unfortunately, the same cannot be said for over-the-counter whitening products, which typically only last a few months.
However, there are certain factors that can affect how long the teeth whitening effects last. Practising good oral hygiene will result in you enjoying the effects for a longer period. On the other hand, things like smoking, drinking dark liquids like coffee and wine will stain your teeth quickly, making the teeth whitening effects short-lived.