I figure good jokes wear out faster than good songs so they need to be changed more often. I think an intelligent and witty introduction can be a pleasure to listen to and I enjoy hearing it. I think five minute explanations of every song in a set as the writer tells you what colour the sky was, the exact time (it was three fifteen..no.. actually I think it was three eighteen in the afternoon)and when his/her bowels moved that day, when he/she was inspired to write this song about peonies, are to be avoided by audience and performer. I think if a song written today, about somebody today, still needs that much introduction for people to relate to it its either too personal or lousy. I like performances that mix up the length of introductions as much as they mix up the songs.