CKK, unlike with the girls, the boys don’t have an arbitrary time that they go to E”Y. If it is arbitrary, we have a great problem with our learning system. It should be an organic part of their program to maximize their growth in learning. For some boys it will be this year, that zman, for others a different one, varying from yeshiva to yeshiva, and from boy to boy within a single yeshiva.
Then, depending on where they go, whom they form a shaichus with, etc. each boy will stay as long as it is feasible for him and his parents, while he is still growing.
If it’s all arbitrary, better the boys stay in chu”l.