Spock is the only source we have for info on this subject. "Every seven years, we are driven by forces we cannot control, to return home, and take a mate, or die in the attempt."
People mistakenly take this to mean the cycle is male. That cannot be. Nature does not create this kind of crisis for mere sexual pleasure. Mating is reproduction and there is no point in driving a male to the point of death or murder if the female is not ovulating. I theorize that orginally there was no mating cycle for the male. Males were able (telepathically) to discern which females were fertile and their obsession was with them. Vulcan cultural bonding of children was an attempt to control this ,so that (seven year estrous?) he was linked to HIS female only. I think that's where the seven years comes in. Perhaps Vulcan women only become fertile every seven years.
Evidently, Spock's bond with T'Pring had not "kicked in." We don't know why really. T'Pring's relationship with Stonn, whether intimate or not seems to have been the trigger for Spock's crisis. Remember, Spock has been missing from Vulcan for eighteen years! T'Pring logically concluded that she was not going to get marriage, and a family from him, so she chose someone else, thinking it would be allright since the bond was flawed. I know she didn't say this, only that she didn't want to be the consort of a "legend" This makes no sense. Spock should have shown up years ago!