I disagree with long courtships/engagement not being a tznius issue (taharas hamishpachah is a very bad analogy), and I disagree with this having any shaychus whatsoever with the divorce rate.
I’m not going to quibble about whether there should be six, eight, or ten dates, but I think it is something decided on an individual basis and there shouldn’t be preconceived notions – not that you need ten, and not that a decision must be made after six. At a certain point, though, there is no benefit, and only risk.
I think if there’s a good shadchan, the longer they stay involved, the better chance the shidduch has to succeed.
Oh, and I despise artificial analogies about age. As far as I’m concerned, if you’re old enough to drive, you’re old enough to get married. Or maybe, if you’re not old enough to receive social security, you’re not old enough to get married – I forget which.