Express your sincere interest and explain that you can't budget more time than that. After the third question, explain that the presenter will be available for questions after the cracker barrel. This establishes a precedence. Becoming a Boy Again Convincing leaders to enjoy campfire singing like boys do is no easy task. Get someone who is naturally enthusiastic to get up and lead a song.
Example is always the best teacher.
Start with a snowball song. They each go to two other people, and so on until the entire audience has joined in. Slow moments in a meeting give people a chance to think about what they'd be doing if they hadn't come. A brisk pace is essential, but you don't want to offend someone by cutting them off. Each district had their own way of addressing this problem.