Long time reader, first time poster. I'm not sure if it's totally relevant to the topic, but regarding affairs due to mismatched sex drives, I can speak from the other side of the fence. I've been married over 12 years now, and for most of that my wife has virtually denied me sex. Before we married our sex life was great. She then developed a thyroid problem during the pregnancy of our first child (we have two kids, so i guess we've had some sex).
The problem has been that due to her medical problem she has just no sex drive whatsoever, and no sensation / feeling down below at all. I'd never let that be the cause of a split as we have kids, but I'll be honest though, it's caused a LOT of arguments and resentment over the years. It can give a real knock to a mans pride to be physically rejected by his partner, and in my opinion, when it's this way round (the woman with the sexual dysfunction), i think it's unreasonable for her to not satisfy her husbands needs. If a man can't get an erection, then there's no sex - but to be blunt here, a woman can just 'lay back and think of England'. I'd always get the "not tonight thanks" reply though, every time.
Anyhow, to try and keep my story short, about 3 years ago i got friendly with a woman at work. I was offloading all my marital problems on her, and it turned out she had a sexless marriage too (and no kids). After much arguing with my wife we got some tests and treatment (Androgel for her), but it just made her aggressive.
We did come to an agreement though, that as long as I didn't demand too much we could make love. But picture the scene - lights off, no touching breasts (in fact she kept her top on always), and "be quick please". But I guess it was better than nothing. Over a few weeks though, she'd fake falling asleep to avoid sex, and i'd have to literally beg her to get it maybe once a week. Until the inevitable happened with the woman at work. On my birthday as she was leaving my room i asked her if i was going to get a birthday hug. That quickly turned into a kiss and, well the rest is history.
The kind of job i'm in made it very easy to have a sexual relationship actually at my place of work, and that's what we've been doing for the last 3 years (no meeting up outside work). It's been on and off though, as the guilt I feel afterwards rips me apart. I know she gets fed up with this, but afterwards I often tell her we must stop doing this. It's difficult though, as she likes to come up to see me for a 'chat' that more often than not ends up with her coming on to me, telling me (for instance) about her masturbating the night before thinking of me. Then it's 'little head' over rules the 'big head' and we're at it again.
If it was just me and my wife, i'd have no problem, in fact we'd have probably separated. But we're a family. And yet I need to feel like a man, and i need sex, and this woman does things you cannot imagine (and lets me film with my phone). It's like a drug, I know she'll let me do absolutely whatever I want to her, talk dirty to her, any time i ask. For me it's just a sex thing, but for her it quickly developed into love. I've explained time after time i'm not leaving my family, and she'll say she understands, but I know she hopes one day we'll be together (we wont).
Anyhow, sorry for rambling on. If nothing else I think my story shows that sex is important in a relationship, and if you aren't satisfying your partner, or she isn't satisfying you, then eventually someone else will. Just lastly I will say this though. Since I started this affair, my relationship with my wife has been much better. Obviously not sexually (we hardly ever now, and i rarely enjoy it when we do), but in other departments (ie we don't argue).
This may sound selfish, but I think as long as I never get caught out, then having an affair was the right thing to do. I know she has hormonal problems, but to just expect me to lead a sexless life because she's ok with that is unreasonable.