i have heard firsthand accounts from a couple of people who claim that a few individual hairs they'd had lasered off ended up coming back a few years later, and they kept needing to go back for touch-up sessions. maybe they were getting screwed over by their hair removal place and actually getting IPL, or maybe they were actually new hair follicles which hadn't been active during the initial rounds of laser?
at any rate that is reassuring to hear :)