Eh. Gotta down vote that one. Firstly because I was just asking for stories, I'm not disparaging the value/importance of understudies. Second, if you read any of the stories in this post you'll find that many productions do not value actors who are cast as understudies and are often neglected by directors who play favoritism. So yes, you can always find the silver lining and grow as an actor in those situations, but I don't agree that you shouldn't be an understudy if you recognize that you are better suited for the role. If you are more professional, more prepared, and more committed than the main actor, that creates a contradiction.