Frankly, I wish your wife would consider that it's a hungry dog that goes after the trash. Sex is part of marriage, that's pretty well established. I think you should jokingly bring up the idea of subcontracting, tell her you have a couple of candidates in mind.

No, I'm totally kidding. She'd go all Bobbitt on your dick. (Problem solved?)

Just so we're clear, I am NOT proposing that you cheat. Don't do that.

I imagine you must have quite the internet porn habit by now. Yes?

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I think all women really want is to be proven wrong about men.