For how long should one go out with a girl before marriage?
Six times is more than enough. But you should ask questions, however. You have to investigate the proposed shidduch very well.
You have to find out, first of all, about her health. You have to find out if the girl is willing to have children – a large family. You have to make sure that she’s willing to live in a frum Jewish neighborhood all her life. You have to find out if she’s willing to be a woman without a career. That she’s willing to be a housewife. Now, sometimes she has to work to help her husband in the kollel for a while. Ok, that’s fine. But she shouldn’t want to be a professional. She shouldn’t want to be a career woman. That’s very important. Professionals, you should know, are not such desirable wives. They should please be מוחל me, the frum professional girls, but still, it’s better a non-professional.
Also, find out if her parents were ever divorced in the past. Sometimes people were previously married and divorced and the wife wasn’t given a כשר גט. And then there’s sometimes questions of ממזרות. So you have to find out how כשר the family is.
And also be sure to find out if she is hot-tempered. Is she too lively?! Too lively – you should leave her for somebody else to marry. With a quiet girl, you’re better off.
Some more advice, I’ll give you privately, if you want.