I got lucky a few years ago and met a woman that had played Zelda and the Sims. I introduced her to WoW and....well she's a pretty amazing disc priest. She does do a lot of research on her class.
What I've found on our server is that the peeps who are progress driven tend to quit after they've "beat the game" and disappear until new content comes out. These people are however a minority on our server. My guild is casz; come and go as you please, no rules except respect your guildies. We've all got our kingslayer titles, got our 310 protodrakes from ulduar, and now have 10/12 ICC bosses down on heroic, with sindragosa I suspect the next run. With the imminent patch and the expansion only a number of weeks away, our timing is pretty good. Having said all this, our core group is small, tight-knit, and we've known each other for over 4 years now. I also don't play everyday like I used to years ago, there are many other games that I'm into, so I don't really get tired of it.
.....I do have to admit that having a woman that plays it a lot does get me to play!