Thomas Schippers asked that question in the Cincinnati trumpet audition in 1975. It was after one of those long grinding excerpts from Ein Heldenleben. I was a bit puzzled, thinking that I had just nailed it successfully. Later I learned that he was testing for endurance.
At Tanglewood one summer we heard it again. Roger Voisin was conducting us on Fanfare for the Common Man. Right before we began the performance, he said "all right, boys, we're going to play it twice." (GULP!) Fortunately, we only played it once. He then smiled as if to say, "just testing you, guys."
Lesson: Once is not enough, even if it's good.