I think a player can. And what I mean by that is when you are playing showcase baseball or attending showcase events you should make sure you are prepared to show your best. I know your not going to have your best game everytime out. But you should be physically and mentally prepared to show your best. I do believe that some kids get worn down by all the travel and playing and need some down time at times. So yes I think a player can showcase too much just as they can do and we can do alot of things too much.
Will coaches begin to nick pick a player if they see him too often? Of course they will. Just as some players if seen enough times will begin to grow on some coaches. So just play the game because you love to play the game. Bring it everytime you come to the ball park. Dont think of it as a showcase. Think of it as an opportunity to show what you can do while your doing what you love to do. And dont worry about the coaches in the stands. They are there to see you. You should not be there to worry about them.