My minimal requirements were:

• she doesn't mind that I have nerdy hobbies (programming, math...)
• she also has some hobbies, so she doesn't require constant "babysitting" from me
• if there is a problem to be solved, I can rely on her cooperation
• she wants to have children in reasonable time horizon

This is probably better explained in negative, as an experience of traits that ruined my previous relationships. At some moment I became able to impress girls, even those I previously thought were "out of my league", by being smart and witty, a good dancer, and having a few interesting stories and impressing achievements in the past. The problem is, it probably created wrong expectations.

I like to go out and dance, once in a while, but I also love to spend a lot of time with my computer or debating "nerdy topics". I can be funny, but I also have some problems that I need to solve (such as procrastination, not being satisfied with my career, etc.). I do achieve quite impressive things once in a while, but my typical day is completely unimpressive (I go to work, come back tired, read some web, and go to sleep). So I guess the things that helped me seduce the girls seemed like false advertisement afterwards.

Seemed to me that the girls I seduced by fun and dancing often expected the whole life to be "fun and dancing". They probably expected the whole life to be just like at the college; at the beginning it seemed like I could provide such life to them, and when I disappointed them, they moved to someone else who seemed he could fulfill the promise better.

For a stable relationship, I need someone who doesn't expect the whole life to be like a college. Someone who can help me solve problems when they appear (and of course I provide the same in return). Someone who can spend their time with their hobbies, while I spend my time with my hobbies.

I got all this, and more. My wife enjoys reading SSC, and we can discuss that kind of topics. We also have similar ideas about upbringing children.

Unfortunately - I'm not sure. It took me two or three months to figure it out in that case, and while I remember the revelation that "This is a healthy relationship", I don't remember anything in particular sparking it.

If this relationship ends, I still don't know what criteria I'd use to identify what I'm looking for. (She messaged me on OkC, actually; perhaps the only woman to do so who wasn't threatening me or who hadn't read my profile at all, although I fixed the latter by making my profile picture deliberately off-putting to the sort of person who wouldn't read a profile in the first place.)