I know of two people in my immediate family from teen relationships which failed to adult relationships when they met again, which succeeded. Apart from that I am going to discount any teen/young adult relationships I know of.
Personally I think its best to let the emotional dust settle with no contact for a while, whether that is many months to many years. Chances are though it won't work. So that's why its important to go NC to stop the confusion and get happy again.