the time they join the troop it is rough. The older scouts aren't interested in doing the Tenderfoot-First Class items again and are focusing on merit badges, plus combined activities, stake activities, service projects, etc. Not to mention if they aren't used to working on rank advancements by then, other interests take precedence.
A passionate (and very very patient) EYO Leader can make all the difference. It is a tough group.
To tell the truth, I would turn in my COR title to be the EYO Leader right now. Well...until my first week and I remember how 11 year olds act. Then I would probably run back to the Bishop and tell him I changed my mind.