Once you're no longer a teenager, who needs awkward sex followed by having to face your wife crying and whatever tension that creates? And Jen stops the minute you come? No round two?
Honestly, if I were in your shoes, I'd say I didn't want to do it this way, it's not worth it. Your body comes but the rest of you isn't that into it. Maybe you can get a better deal out of it, like more enthusiasm from Jen or some participation from your wife. Ask your wife to suck your cock just before you go into the bedroom with Jen. Now that'd be a memory to have.
