Yes, 5 minutes seems perfectly doable

"Hell yeah, I'll take that bet," I say, my judgement clouded by the thought of Becky stroking my cock. "If I win, you need to join me in being naked on this nude beach!"

"Fine," Becky agrees. "But if I win..." Becky takes a moment to think. Her roving eyes land on a piece of silk string that had been used to roll up our beach mat. She grabs it and holds it up in front of me. "If I win, I will tie this string around your cock and balls like a leash, and you need to follow me to the beach bar."

Becky grins wickedly at me. I frown: it's clear to me that the weight of our wagers are not equal. But the thought of being pulled along by a leash around my genitals by Becky... it makes my cock twitch with excitement.

"Deal," I say, and Becky and I shake hands.

"Alrighty then," Becky chirps, wasting no time to immediately kneel down in front of me. I'm taken aback at Becky's enthusiasm, but my surprise vanishes as she grabs my cock.

"Sue, you have that timer ready?" Becky calls out. Behind her, Susan holds up her smartphone with a timer displayed on the screen. "Ready, Becks," she says.

"Then let's go," Becky looks up at me, grinning, as she starts to stroke my cock with her hand. Susan starts the timer and she joins Samantha in watching Becky stroke me off.

It quickly becomes clear that I've overestimated myself: it doesn't take long for me to start biting my lip to prevent myself from moaning out loud. Pre-cum leaks profusely from the tip of my cock, and Becky uses it to her advantage as lube, allowing her hand to slide smoothly up and down my shaft.

"Fuck," I gasp, clenching my eyes and fists and I struggle to maintain my composure.

"Having trouble, John?" Becky teases, a confident smirk on her face. Without waiting for a response, Becky spits on my cock, following it up by focusing quick, short strokes on my cock head. Her technique coaxes involuntary moans out of me, betraying my pleasure.

"Ohhhh, he likes that," Samantha remarks, watching us closely. "He likes that a lot!"

"Don't forget the balls, Becky," Susan calls out.

"I know, I know, Becky snaps, using her left hand to fondle and massage my balls while her right hand continues to rub my cock head. The combined effort is slowly bringing me to the point of no return, and I'm finding it harder and harder to focus.

"Don't try so hard, John," Becky crooned at me, "You might hurt yourself. C'mon, just cum already. Cum all over me!"

The thought of covering Becky with my hot sticky spunk proves to be my undoing. With a mighty groan, my body arches as waves of pleasure surge through me, followed quickly by long streams of thick cum erupting from the tip of my cock.

The first stream of cum splatters across Becky's face cleanly, causing her to squeal. But she quickly angles my cock away from her face as she continues to stroke, milking my cum onto the sand beneath us.

"3 minutes and 42 seconds!" Susan exclaims, checking the timer. "Becky wins!"

As my orgasm slowly subsides, I look down to see Becky watching me, a single streak of my cum across her face, giving me a shit-eating grin.

"And that's how it's done," she says, standing up in triumph.