7 Earth years or 7 Vulcan years. Say there were 420 personnel aboard the Intrepid. That would mean 60 would have to go home to Vulcan every year. More than 1 a week. OK while I believe that Vulcans can have random relations what is Spock saying to Droxine? Like I have to have wacky sex every 7 years and you're too delicate for it. Or umm there's a rumour that Vulcans can only have sex every 7 years and I'm going to exploit that rumour to get rid of vacuous Droxine avoiding a diplomatic incident.