There's a mixture of relief and regret when Spike's teeth finally release his throat, and a shiver at the cool tongue laving the tender skin. Jack's such a whore for sensation, and danger, and pain, and - oh god, so many things. This'll do nicely for now, though, especially with Spike's fingers combing through his hair, and if Spike wasn't already aware that that's another thing he's a whore for, the way he's humming happily - almost purring - will let him know.
He laughs softly when Spike echoes his assessment, and presses a smiling kiss to Spike's temple before letting himself slide off him to one side. He's a heavy enough man that it's an instinctive move so as not to crush his partner once the first intense aftermath is over. He's also not used yet to having a partner who doesn't need to breathe.
He rubs a hand over his face and then looks round at Spike, beaming broadly. "Thank fuck. I was starting to think we'd never get there!"