You can’t compare to the outside world. From what I understand, the reason so many people get divorced after living together a long time is that they get married to hold the relationship together. Usually after a few years their relationship is failing and they want the next step – children or marriage – to hold them together. It fails because the relationship was already failing.
Divorce should NOT be stigmatized otherwise you will have people stay in terrible abusive relationships.
IMHO, relationships succeed when both parties want to make it succeed and both parties have good chemistry (meaning, how they interact with each other). If you both WANT to make it work then you can. So long as the basic chemistry is there (if you don’t like a person, how can you deal with them?)
I personally could not marry without really knowing a person. I dated my husband for 1.5 years and we were engaged for 9 months. We were in school together so we spent a lot of time together. We were also very honest with each other (especially about our shortcomings and life goals) and were able to hash out a lot of issues before getting married (we came from somewhat different backgrounds so there were issues to discuss).
I don’t think short dating is a definite cause, but it could lead towards someone making the wrong choice based on a lack of information.