If people aren't eating the food — chances are something is wrong with it. It could be lack of salt. Perhaps the bread component is now soggy. Maybe the cold thing is now warm, and the hot thing is now cold. Pay attention to the food, and make changes if necessary. Prepare enough dishes to satisfy the hungry crowd, but if the flies start taking bites before the people do, hold back! We don't want to consider how many trillions of microorganisms are growing on the beef tartar that is now room temperature.