One thing you ladies might like to know about my worldbuilding for this novel.
I have it that to achieve and maintain an erection, male vampires must first drink. The intake gives them a bloodflow, much of which is diverted, naturally, to the penis.
They don't ejaculate, having no fluids of their own, but they do experience an orgasm of sorts. They definitely reach sexual fulfillment, but it doesn't stop there. They basically keep going until the earlier intake of blood and its effects fade away, bringing their bloodflow to a standstill.
I've compared Jonathan to the Duracell bunny, if you have those commercials in the states? He goes until his circulation slows to a stop, or until his lover gets too sore.