I have a 2010 Macbook and cover is starting to crack by the hinges. I have considered taking it in and see if they'd replace it but, I'm going to slap a small hard drive in it with a fresh install and let them have that.
I don't have anything bad, I just don't want people seeing what is none of their business to see.
To answer your question: It'd probably rely on the on the integrity of the rep at that time.