Yep, all of this. Let's be honest, after U15, playing at the highest levels (ECNL,GA,MLS) gets to be a brutal affair for kids and it becomes harder for parents to accept that culling of the herd is happening. Sharing playing time between 2 keeps is tough - It happens but it's rare that you get two top keepers on the same team beyond U15. You could argue that roster #s 16,17,18 are $$$ players and will struggle when on the field. It's likely, like stated above, that there are better players one age group down that will be better served to play up once in a while. Playing up is effective if done for the right reasons and to the right player.