Almost an entire day.

Amy keeps it up without fail. Her stamina is amazing. On your end, your tits kept producing milk. Despite that, they have doubled in size from your generous FF bustiness that you had before you started this. They luckily didn't grow long but instead puffed out and to the sides. You do notice them resting lower the past hour, however, as their size must be growing in all directions now. In your ass feels like several hundred pounds of cum and milk. Amy finishes cumming again.
"Full!" Amy exclaims, and sits on the couch in front of your face. You lick the butt cheeks pressed against your lips. "You sure got busty," she says as she leans back against you.
"Like it?"
"Sure do! You'll notice my balls grew at about the same rate as those boobs you've got. These sure are getting to be a bother to lug around. How do you guys manage. Flopping around, swaying madly about...these things are a hazard!" She stands up and flops them heavily in front of your face. "See? They are so big!"
"I'll tell you the secret if you tell me yours. So how do you lug around these big things up top?"
Amy bends over and presses hers to yours. "Mine were never this big, remember? I didn't even need a bra, really. So I guess I'll need to learn to deal with my...erm...front-heaviness on my own."
"It's called a bra...get one," Blue interjects before you can continue the conversation.
"And for balls?"
"A specially made thong with cups for the balls," Red answers.
"Why does it have to be a thong and not regular panties?"
"Because it leaves you as nude as possible and your ass open to invasion while providing the support you need."
"Oh, nudity and ass invasion I understand. So what about this cock? It's like two feet long now and as thick as my thigh!"
"You have several options, Mistress. Tuck it between your butt cheeks, pull it up between your tits, stuff it down your pants or shorts leg, or just let it hang free in a dress."
"Shorts leg? It wouldn't do much considering how short my shorts are..."
"So," you chime in.
"So my options are tuck it or conceal it, both seem like I wouldn't be able to actually hide it."
"Not one of that size, Amy," you tell her.
"Either way, I wouldn't be able to zip up the front of anything. Let me show you," she runs off to grab something. Her cock slaps her thighs as she goes, flinging drips around. She returns in a pair of her short shirts. Well they must be her old ones, as she looks very constrained. Her zipper is open and her balls hang out of the open front. Her cock hangs out one of the "legs" which only go an inch farther than the base of her cock anyways. In the back most of her cheeks hang out of the top of the waistband, with only the bottoms resting in the denim garment.
"See?"
"I don't see a problem with that," you say.