I think ponn farr is a young man's syndrome, something like puberty but it recurs a couple of times.
Actually, VOY "Gravity" sort of suggests it only becomes worse with age. At least if it goes untreated, one way or another...
I'm pretty sure it's stated in Amok Time or ST: TSFS, Vulcans under go Pon Farr every 7th year of their adult life.
"Amok Time" makes no mention of a seven-year cycle. "Cloud Minders" has this exchange, though:
Droxine: "You only take a mate once every seven years?"
Spock: "The seven-year cycle is biologically inherent in all Vulcans. At that time, the mating drive outweighs all other motivations."
We don't get an exact description of what this seven-year cycle is, but it seems to be related to this "taking a mate" thing Droxine asks about. It doesn't follow that Spock would experience this full pon farr thing every seven years, though - merely that he'd have a strong urge to find a mate every seven years.
It's not until ENT "Bounty" that we hear for certain that females get pon farr, too (Spock was gender-unspecific in "Cloud Minders" but that wasn't explicit enough yet, and he might not have been talking about pon farr in the first place). But "Bounty" fails to tell that pon farr would happen every seven years; it's just something that hits T'Pol at that time, with no mention of it possibly recurring. (Circumstances cause it to hit T'Pol too early, though: she says "it's not time", as if she knew when to expect the phenomenon. But she never says she would have experienced it before.)
So, as far as we can tell, pon farr may well be a once-in-a-lifetime experience for Vulcans of both genders, coinciding with the seven-year mating cycle but not being an integral and recurring part of it. It's merely the crowning moment of your mate-finding urge, perhaps hitting you on the very first round of your seven-year cycle, perhaps lurking until some later round.
Spock experienced it only once AFAWK - until being reborn, at which time he again only apparently experienced it once despite supposedly maturing through several decades. Vorik experienced it once (VOY "Blood Fever"), perhaps because he had no mate yet. Tuvok experienced it, too, despite previous experience, but perhaps because he had no telepathic connection to the mate he already had. His still remains the only confirmed case of a repeat performance of pon farr...