I guess I don't really believe in the concept of "the one." There are probably thousands of men who I could have built a happy life with. Sure, he wouldn't be EXACTLY like my husband, but the central qualities that my husband has that I was drawn to are not unique to him.
In my opinion, you should know in a few months whether or not someone has the qualities you want in a husband, as your compliment and help-mate--someone who makes you a better person, who challenges you, while supporting you. Someone that YOU help to be a better person. I think that dating too long can actually be stifling to commitment, as the little personality flaws that we ALL have, and our idiosyncracies can start to look like a big deal to our partner, when they really don't alter who we are at our core. They can become a justification to end a relationship.
I say this because I have seen my brother do it--find a girl that he really likes, that he has a ton in common with & the same core values....but then he freaks out when they start to see his flaws, and vice versa. That is where the commitment comes in. When they see your flaws, and rather than knock you down or exploit them, they help you to overcome or work on them.
This is my opinion, as a woman. Perhaps men, however, have a different thought process.