While I'm a stickler for routined shows and scripted patter, repeating can sometimes be a problem.
Remember, an effect is just an effect. If you present it differently, it's a whole different trick.
When I'm working with teenagers, though, particularily if it's a longish show, I'll often include a little request section in the middle. That way, if people know me (and a lot of people remember my shows
) they can ask for something they really like I may have left out otherwise. Always be ready to play ball with your audience. They're the ones that wind up paying you.