This is a very common question, not only with Fraxel, but with all forms of rejuvenation surgery. Fraxel will turn the clock back, but the clock starts ticking right away. How fast you age is mostly determined by your genetics, and exposure to sunlight and tobacco smoke. I personally had Fraxel done last year and I plan to have it done again in a few years when I become unhappy with the return of the signs of aging.
After the first series (usually 3 or four) of Fraxel re:Store treatments I have found that most patients are happy with a maintenance of one procedure once and occasionally twice per year.