Longevity of Teeth Whitening Treatment Results?

Longevity varies from person to person depending on many factors. Host factors would include diet, habits and age. If one drinks a lot of coffee and red wine, you should expect a shorter duration of whiteness. If one smokes, same thing. And teeth get yellow over time as one ages. The pulp of the tooth shrinks, leaving behind more dentin and a more yellow appearance.
Teeth whiten with gel differently based on frequency, duration and concentration. Whitening processes vary in longevity based on depth of effect. Some products are fairly superficial and don't last as long. Processes that are brief will not penetrate as deeply as processes that exposes the teeth to the gel for long periods of time
All whitening should be maintained over time, some people every 6 months, some people avery 3-4 years.

Teeth whitening maintenance needs to be done on a regular basis which usally is every six months.  Much like keeping a youthful face with facials, and a tan year a round by going to a tanning salon, teeth need to be whitened periodically to keep them white. If you practice good oral hygiene habits and brush with a whitening toothpaste and avoid foods that stain your teeth, maintenance will be easier.  Age also has a bearing on how white your teeth come up. Older people have a harder time than younger people . Unfortunately, age affects the whole body including your teeth! 

Teeth whiten to a different degree for each patient. That being said, each patient should expect the whitening process to last differently as well. Depending on what you eat, drink, and the habits you have, like smoking, determine how quickly your teeth will become stained again, but understand that there are ways to keep you teeth whiter longer after you have had them whitened.
I recommend that each of my patients whiten their teeth, top and bottom at the same time for an hour or two each month, with the take home trays that we have made for them. This does not stop the staining process altogether, but certainly helps to slow down the natural staining that will occur over time.

Teeth generally get darker with age. The enamel gets a little thinner and smoother reflecting less light and allowing more of the dentin to show through. Since the dentin is where the tooth gets its color, you need to get the bleach down deep into the dentin to remove the color. If your teeth bleach quickly you might not have to touch them up as much, but if it takes along time, you may need to touch them up quite often.
Stay away from dark liquids like colas, coffee, black and green tea, red wine, etc.

If you drink a lot of coffee, tea, red wine -- other staining beverages or foods -- your whitening results may fade a bit. However, it's easy to re-whiten. If you use custom trays for whitening, you might want to pop the trays in for a couple of days in a row every 4 or 5 months. That's all there is to getting your teeth back up to their optimum whiteness.

It's like asking how long will a tan last. It's all about maintanence and diet. You need to use a whitening toothpaste and mouthrinse and try to stay away from dark staining foods like blueberries, etc. Everyone I know does touch up teeth whitening every 6 months or so even after professional teeth whitening.

The longevity of Teeth Whitening depends on your diet and your lifesyle. If you eat food rich in color you will need to bleach more often. To get the best result one should bleach his or her teeth every 6 months for a day or two. After you initially bleach your teeth wait about a year and then bleach them with custom trays every 6 months after your prophylaxis for 1 or 2 days an hour each time. Bleaching too often can damage your enamel and weaken it.

Much like working out to stay in shape, tooth whitening maintenance needs to be done on a regular basis. If your habits that caused the staining remain the same, i.e, you still drink coffee, tea, red wine, or smoke or eat other staining foods on a regular basis, your teeth will restain. If your teeth were very dark to begin with, they may require more regular maintenance to maintain their new bleached shade.
The good news is that for most people, if they have an in-office treatment (for the best results, it should be more than just ONE in-office treatment and it should be combined with an at-home bleaching protocol during the initial treatment), maintenance can be as simple as using their take home bleach in their custom whitening trays one day/night every few months. Wouldn't that be great if that would work with personal training as well!