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.
Labs are quite possibly the most important part of teaching scientific concepts.
I feel like if a lab is worth doing, it should be important enough to spend a lot of class time on for both the inquiry part and discussion of results.