Peter Mead over at Biblical Preaching has an interesting post re: illustrations. He notes that their is a hierarchy of illustrations and some require more time in preparation in set-up and delivery. He begins:
Robinson and other instructors teach a hierarchy of illustrative materials. In a simplified four-level hierarchy the list would be as follows:
Level 1 illustrations come from the experience of both the speaker and listeners.
Level 2 illustrations come from the experience of the listeners, but the speaker has to learn about them since they have not personally experienced the same.
Level 3 illustrations come from the experience of the speaker, but must be learned by the listeners.
Level 4 illustrations lie outside the experience of both speaker and listener.
He goes on and describes the process well. You can find the full post here.