At my CPs gym (which is mid-sized so some and large to others I guess) it seems like crossing over is the rule instead of the exception. I think that the parents push more for it than the coaches do. Last year I think there were only 3 or 4 girls on her mini 3 that didn't cross to the youth 2 or the youth 1. The girls from the youth 2 were mostly crossovers from the mini 3, youth 3 and youth 1. I think there were a few girls that were solid youth 2 that couldn't be on mini 2 for age and didn't go up to senior 2 because of age as well. Some parents get pretty irate when you place their athlete on a lower level than what the athlete is truly capable of doing. The gym tried really hard to make sure there was an appropriate team for everyone.
This year started out differently. The original placements only had a few crossovers. I sat at a parent meeting and listened to parent after parent request that their athlete be allowed to cross-over for various reasons (flying was a popular one, but also many of the younger athletes liked their lower level teams because they were less work for them and therefore more fun). It seems like it is the gym culture to "live" there. It is not at all uncommon for athletes to be at our gym 5 days a week.
When your CP really loves to be at the gym, crossing over is really a great bargain. Some gyms don't charge at all for crossing over and our gym charges just an additional $30 a month for what could be an additional 4 hours of practice a week.
My CP is only doing one team this year and she is kind of disappointed, but I don't have the time this year to spend as much time at the gym as we did last year...