Oddly, those with shorter dating have longer marriages.
I wish to add that it is nearly impossible to prove that dating for a shorter amount of time is an indicator of a better marriage.
Since the groups who date shorter have many sociological differences, the disparities would need to be controlled for. That would be impossible, unless people from each group agreed to be part of a massive social experiment, and since the people who agreed would be self selecting, it would still be inaccurate.
It is possible that if frum Jews were to date for several years and then have a multi year engagement, it would result in even better marriages. (I am not advocating it.)