What Riley hungers for is hunger. He loves to see Sandy's teeth slowly lengthening; and he tries very hard not to bring any psych theory to that particular enjoyment. He loves her lip-licking, the thoughtful flicker of her tongue-tip in the corner of her mouth as he sits on the dingy mattress, digs a crumpled twenty out of his pocket. He loves the little moan that escapes her sometimes as he rolls up his sleeve, slowly, carefully, stretching out that moment of being her focus, her tunnel vision, her necessity.
Buffy moans with fulfillment, sometimes. But never, never with need.