A typical event is either 3 to 4 hours long. The client can choose the length of set they need. Typically during a 4 hour event the performers will play 45 minute sets w/ 15 breaks or the client may choose longer sets such as 2-90 minute sets with a 30 minute break. (this is perfect if there are announcements or presentations during the event)
A music coordinator will help you decide what will be best for your event. The bands always provide pre-recorded music to be played during their breaks so there is never silence.