America is obsessed with youth. We all want to look young forever, and vampires do. They are caught in their prime, if that's when they've been turned. And they'll be that way forever.
A more important reason is that the bands will intuitively trust someone they think is a peer, and who speaks fondly of the same formative rock and roll experiences.
The songwriter mustn't fall in love with his own song. If it doesn't belong, he can't push it into a show. Let him save it; maybe it'll fit in another show.