Labs seem incredibly important for an inquiry-based classroom.
Some teachers stop doing them because of management issues. Three days per lab is one way to plan - day one for preparation and exploration, day 2 for the actual data collection, day 3 for analysis and communication. My CT is a firm believer in labs, to me it seems that she plans her lesson content around labs. These labs usually take 2 days, with the first day of inquiry and the second day with gathering data and closure. She also includes other inquiry activities that include the students becoming physically involved.