There's a possible catch to this entire discussion. It has been suggested that sex, with regard to Vulcans, initiates a mental bonding. Doesn't this further suggest that Spock didn't have ?sex prior to 'Amok Time', since he had to go to Vulcan for T'Pring and be bonded with her, whether physically or emotionally? But what about Spock's relationship to Leila Kalomi in TOS' "This Side of Paradise"? They had a past relationship to the episode and the episode itself predates "Amok Time". While it is never shown, I was fairly certain that Spock and Leila furthered their relationship in "This Side of Paradise". Now Spock was under the influence of the spores and this may or may not have had an affect on his cycle of mating. But this additional relationship of Spock's should be factored into the overall equation.
I've written about it on TOS board, but IMHO Spock and Leila didn't have sex. Remember that spores' influence stopped in case of strong emotions (hence Kirk's insults and fight with Spock), and having sex (maybe for the first time) would be quite an experience for such a reserved logical Vulcan, even in his drugged state - drugged but peaceful. In this episode Spock behaved like a very young teenager, was climbing trees, kissing the girl, rebelling against his captain. Like he was rather childish thirteen years old. I seriously doubt there was more than that, even though he changed clothes and Kirk was speaking about 'making love' (but I assume he wasn't peeping ). In this episode ?Spock was peaceful and content with Leila's presence, not passionate towards her.
I think he matured sexually during Amok Time.
He certainly had sex with Zarabeth, though, but that was much later.