also by limiting the open mike time, you are still not discouraging them to continue to work on their music. One thing they do here in town at the concert in the park series is they allocate time. Some people get a half hour, others get a song .. no one ever complained. I think it is a great Idea, if someone asks why so and so gets a half hour or 45 minutes the organizers say because they are very popular with the audience. That doesn't make others upset at all and i like that approach. I have seen people come back to do their 1 song again and again but it gives them a chance to perform out and the audience doesn't have to suffer through a whole set either. Yet those the audience really really like get to hear a bunch of their music ... seems like a good approach that works here that you folks may try