Endurance Training -- Females Wanted

My latest craving is focused on the concept of endurance training. Whether it's within the bounds of a D/s relationship, a twisted marriage, or a starstruck fan/celeb relationship (or anything else you can think up!), I love the idea of a woman who is sexually needy and forces her partner to train up to keep going as long as she can. Toys could include cock rings, milkers, electrostim, cock pumps, and anything else you might want to include. Although it's not necessary, I'd also like to see some juicy penalties if he fails. Nothing is really off-limits here except for snuff, but some items that seem especially appealing would be making him watch as she fucks other men (potentially with fluffing/cleanup duties attached) or CBT. Please reply here, PM me, email me, or IM me if you're interested--I'm flexible!