Let's not forget that sometimes it's pure egotism that makes some people sing a long song. They want to be the center of attention for as long as possible. It's normal to want attention, but it can be overdone.

Is your audience looking bored and resentful? Not making eye contact? Are shoulders hunched, do faces look stoney? Do people suddenly need to go to the bathroom? Then it's time to cut out verses 7-16 and get to the end of the song.

I remember one night long ago, when a group of us were singing songs in a Catholic coffeehouse. It was midnight or one o'clock, and we were all getting tired, but didn't want to go to our lonely rooms just yet. A young woman from Chicago (this was in Wisconsin, so naturally she was from Chicago) who was bigger and better dressed than any other female present, stood up, planted her hands on her hips, towered over us and began an interminable version of "St James Infirmary." I wanted to sock her one.

At the time I thought of her as a show-off. Now I think she just a bully.