Keeping it white
Six months to two years — you decide which. The first 48 hours, the two-week bounce-back, and the three places stain comes from.
Whitening is not permanent. Nobody tells you that on the box.
How long it really lasts
Six months to two years — you decide which. The first 48 hours teeth are porous and pick up stain fastest. By day 14 expect half a shade of bounce-back as teeth rehydrate; judge the result then, not on day one. Stain comes back from three places: dark liquids, tobacco, and plaque that holds stain against the tooth.
The five habits
The 48-hour white diet — nothing you wouldn't spill on a white shirt. A straw for the dark stuff; rinse with water after hot coffee. Brush before the coffee, not after. Keep your cleanings. And touch up, don't restart: one night of gel every two to three months holds the shade.
Do this now
Pick your maintenance night and put it in your calendar. Still not sure what's right for your teeth? That's what your plan is for.