I didn't go to the concert to get away from the con! Staying at home as I was, I barely felt I was attending Corflu anyway. Though I have been known to do such things, both as a break and from the attractive power of the concert. At some large cons, the dinner and early evening hours are slow (unless there's a program item you particularly want), and coming back from a concert just as the parties are really warming up can be a perfect way to spend the evening.