They last for a year. You can call in on the day of expiration or earlier to extend it another year. I had one certificate from Jan 2009 that I ordered as one of three travel packages before the great devaluation of Jan 15, 2009. I was able to extend it once for free after the devaluation, and I had to pay the difference for further extensions (an extra 50k points one time for the post Jan 15 2009 price). I extended this certificate three times from the original issue before using it this past November.