I was going steady for two months one time, before my SO's husband came home. This also goes for children. I personally haven't run into very many single moms pretending to be sirens in the night, but it does happen. I also don't care if my intended has multiplied herself, but you might. In any case, it's a big thing to lie about.
Many women have serious emotional problems.
You should familiarize yourself with what paranoid, histrionic and narcissistic neuroses are, and pay particular attention to what a Borderline Personality disorder is. You WILL meet them, and they hide it well at first. Consult the DSM IV in a Library, and read about this. They have decided that they aren't attracted to you don't want to form a close relationship with you. This damages your emotional integrity and wastes your time.