My own understanding is that laser is billed as permanent reduction because it can't guarantee killing off all of the hairs - but the ones it does kill, stay dead. It can look like places were able to regrow "killed" hairs b/c some spots have lots of hair follicles and the growth cycle is pretty long, but in reality laser is as effective at killing a given hair root as electrolysis. The catch is that, unlike electrolysis, it's not as precisely targeted so not all hair follicles will be hit. Basically, it's a question of whether the "survivors" left are enough to cause problems.
In any event, the suggested plan is exactly the one I chose for myself, and I got lucky. 6 sessions of laser and 2-3 touch-ups and 99% of my facial hair was gone and I haven't needed any electrolysis so far after all. (It's been about five years, too, and no regrowth yet. I did have maybe a dozen hairs that survived the initial laser, and it just hasn't been worth it to me to seek out electrolysis and deal with the hassle and expense when plucking them once a month works fine.)
I actually did crunch the numbers and decided that at the price I paid, it was also likely to be cheaper to go back for more laser every 5-10 years for the rest of my life than to pay for electrolysis of my whole face. So far, so good.
http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/SurgicalandTherapeutic/ucm142607.htm"Several manufacturers received FDA permission to claim, "permanent reduction," NOT "permanent removal" for their lasers. This means that although laser treatments with these devices will permanently reduce the total number of body hairs, they will not result in a permanent removal of all hair. The specific claim granted is "intended to effect stable, long-term, or permanent reduction" through selective targeting of melanin in hair follicles. Permanent hair reduction is defined as the long-term, stable reduction in the number of hairs re-growing after a treatment regime, which may include several sessions. The number of hairs regrowing must be stable over time greater than the duration of the complete growth cycle of hair follicles, which varies from four to twelve months according to body location. Permanent hair reduction does not necessarily imply the elimination of all hairs in the treatment area."
