The duration of interaction in speech style depends on the intent of communication, such as the length of speech required or the audience being addressed.
Informative speeches: Teacher explaining earthquakes, Student presenting research, Travelogue about the Tower of London, Computer programmer discussing new software.
Demonstrative speeches: Becoming an organ donor, Improving health through better eating, Addressing the negative influence of television violence on children, Becoming a volunteer and making a difference.
Entertaining speeches: Excuses for any occasion, Explaining cricket to an American, Buying a condom discreetly, Things you wouldn't know without movies.