When is it time to take off the training wheels?

Jonathon Mayo wrote a nice article about Cleveland Indians' prospect Adam Miller who is currently pitching in the Caribbean League (here is a link to the article:  http://mlb.mlb.com/news/article.jsp?ymd=20090109&content_id=3738912&vkey=news_mlb&fext=.jsp&c_id=mlb).  In the article, Mayo quoted Cleveland Indians' farm director Ross Atkins saying "We are as conservative as any team when it comes to that.  We don't over-expose anyone."  This is in regard to Miller's progress which has been hampered by injury.  Miller is 24 and has been at triple A the past 2 seasons due to this injury.  Now, having nothing specifically to do with Miller, but it made me pounder the question "When do you say enough is enough, go out there and play or move on?"  Yes, I realize it is complicated sometime but Mike Knapper from MiLBRadio.com who is a huge Indians fan has seen prospects in the Indians system that are "has beens" before they even make it to the Majors.  So, if a player is healthy, the scouts say he can do the job, the experts all agree, when is the right time to pull the trigger and give a kid a shot?  Hopefully for Mr. Miller (and Knapper) that will happen in spring training 2009 as the Indians open up a beautiful new spring training facility in Arizona.  http://www.MiLBRadio.com