I have used the Crest whitening strips, the Bright Smile laser whitening, and the dental bleaching trays . I do not smoke or drink coffee or tea. I rarely even drink a soda, so my teeth were not that discolored. To me they looked like buttered popcorn, but my dentist said they were very light on the color scale.
The Crest Strips I used about 2 1/2 years ago. I used them for about three weeks before we went on a cruise. I could see a difference, but my teeth were not as white as I wanted.
Then I did the laser whitening at the dentist. It was $500, but my dentist is my neighbor and good friend so we worked out a trade for his wife's nails. (I own a salon.) It hurt!! I did it in the winter and we were going to a Christmas lights show that evening. My teeth are generally not sensitive, but I had to hold my hands over my mouth to try to warm the air up before it went past my teeth! My teeth hurt for several days. I was not overly impressed with the whiteness, but several of my customers noticed. I would never pay for this procedure. After about 9 months my teeth were back to where they were.
Now I have the dental trays. Where I live in GA it runs about $275. I used them every other or every third day for about three weeks. My teeth got incredibly white. They were a little sensitive, but nothing unbearable. I use them maybe one night every four months now to retain the whiteness. The bleach lasts foever, I think, if you store it in the refridgerator. The trays should last forever if you store them in their case. Extra bleach runs about $30 for four syringes full (8 uses.)