Ruby gets another round of medicine

An hour into the movie you start to get hungry and go make dinner, leaving the girls alone. You are a pretty good cook, and you whip up a salmon filet and pass around plates while you finish the movie. Maddy surreptitiously snakes her hand under the blanket and into your pants, slowly stroking your cock without drawing any attention. You do the same, lowering your hand to her pussy and sliding two fingers in. You have been married long enough to know exactly what she likes, and soon she is trying her hardest not to squirm in her seat. You glance at your guests, hoping they haven't noticed, and you realize they are doing the same thing, but less subtly.

You are mesmerized by the rise and fall of Ruby's breasts as her and Becky finger each other. Laughing to yourself you pull your blanket away and toss it to the ground. Maddy starts to pull her hand out of your pants but you grab her wrist and nod towards your guests. They are too absorbed in each other to notice.

You watch as Becky tenses up and begins shaking, moments before Ruby does the same. The pair lean in to kiss each other and you whisper to Maddy.

"This is pretty hot, but we should probably stop. We don't want to waste my cum." Maddy nods and smiles as you continue your ministrations. She pulls her hand from your pants and rubs your leg as you get her off in front of her ex girlfriend.

"Uhhh. Jim?" Ruby is laying back on the couch, eyes closed, hands still hidden under her blanket, looking dazed.

"Yes Ruby?"

"How long should it be between loads until I start to crave it again?"

"Well, it depends on how far the disease has progressed. Without blood tests I can only guess where you are, but I would estimate that you can go 10 hours max, 8 hours to be safe, but you will probably start to feel the craving after about 5 or 6 hours."

"Okay. Only, I think I must be farther along than that, because it has only been 3 hours and I am starting to feel it." Ruby opens her eyes and meets your gaze. "I want to suck your cock again."

"Shit. If you are this far you won't be able to safely go more than 6 hours without swallowing my cum. There is minimal research on this aspect, but one study did seem to indicate that orgasms without ingestion can speed up the onset of cravings, but." Ruby gasped.

"Oh fuck, really? So I can't even have normal sex with Becky?"

"You can, it just needs to be accompanied by you getting a fresh dose. Meanwhile, the cravings may be coming back but you can still go a couple more hours without it. It might be better to wait until we are ready to retire for the night. What do you think?"