Yeah this never set well with me. Unstable planet, unknown life signs heading their way, their ship was just blown to smithereens but those selfsame approaching life forms (something Saavik would have put together) and they do the Sehlat with two backs because of Pon Farr? Forgetting that it leaves out essential aspects of it (the joining at the young age, etc), it's impractical.
At best, Spock got a handy, but I rather think Saavik cooled him off with something more intimate on the "telepathic Vulcan way." Then took a nap.
Honestly, if there was one scene I would lose from the movie, that's it. It's a sweet scene, but it's a bit of a botch.
Besides, and this is the part everyone leaves out....Spock didn't mate in Amok Time. He went through the blood fever, did the combat to the death, thought he killed his best friend, lost his mojo for T'Pring and off he went. He didn't die by not having sex (no Star Trek fan has). It's not important, apparently, that Vulcans mate...they need to defeat the urge.