Great idea for 2 reasons (IMHO)
1) girls should wait till 20 before plunging into adult life, where there are no “do-overs” and mistakes come with a steep price to pay. Let them learn about life, and be better prepared to face what marriage really entails.
2) Since boys enter the shidduch market at 22-23, they SHOULD be dating girls that are 20. Its a sad comment on our boys, if they see an 18 year old as their peer.
And for the record, I speak from experience; I was a 21 year old, the Mrs was 19. Though its been 20+ years, I think I would have made less mistakes (some very costly) had I been somewhat older. Can’t speak for her, but I know I said / did some dumb things, all because of a lack of maturity