We have seen several young people date the same person for years, waiting until they finish college, or until they are "old enough" to marry. (I'll leave the failures of the dating system for another post. Right now, I'm focusing on the waiting and waiting and waiting to marry.)
If they aren't mature enough to marry, why are they considered old enough and mature enough to date? If a guy doesn't even pay his own car insurance, why is he considered ready to hunt for a marriage partner? If a girl doesn't know how to cook or plan a menu, why is she considered ready to start searching for a good husband?
If one of our children finds a suitable spouse when they are 19, we will not encourage them to wait, nor will we encourage a long engagement. If, on the other hand, one of our children is not ready to marry, based on maturity, we will discourage them from courting anyone.
[I should preface this with the fact that we are preparing our children for marriage already. Isaac mows the lawn, takes out the trash, and opens jars for me ;). Maya knows how to cook more than half of the meals on our rotating menu. I am now her Sous Chef.]
Waiting to marry when you've already found the right future-spouse is setting yourself up for moral failure. King David fell into sexual sin. The mighty Samson fell into sexual sin. King Solomon fell into sexual sin. I'm not naive enough to think my children are stronger than these.