Timekeeper, timekeeper, timekeeper
Panelists often have a tendency to drone on and on and there is nothing worse then a panelist who dominates the rest of the participants. Come prepared with a friendly, red card, or a little white flag...something you can wave to (in a friendly way) make the strong point that time is up. If they resist, just cut em off...you can do that without being rude just make some wisecrack...done it many times 😉
Good luck and have fun!