I was married about a year after college, which was the perfect time for both my husband and I. We couldn't have gotten married earlier, we both had school and things we needed to finish for ourselves. It's not a matter of just meeting the right person, it's a matter of not really knowing who you are in your teens. Most teens think they have themselves all figured out, but people change a lot in just their 20s alone.
My parent's got married when they were 19 and 21 though, both went on to finish college and are very happy together.
My in-laws met in highschool, they dated until after college then they got married. They're both very happy together as well.
I don't see the point in not waiting, until your early 20s or after college. If it's true love, it can wait years without being lost. The relationship will most likely be even stronger than it was before if it's something tangible and secure. Marriage should be 100% positive. Teens might think they're 100% positive, and Romeo and Juliet is a wonderful story, it's just not very practical.
That's just my opinion though.
I enjoyed your description of Doris Lessing's "Flight."