To answer your question very briefly, events occur over the course of a year where members can decide together if they will need 24 hours, 48 hours or 72 hours, based on the work of the House, statutory holidays or a number of other considerations. The members can decide amongst themselves, once a report has been completed, how much time they will allow to dispense with a dissenting opinion.
I don't see how we can agree on 72 hours as a firm time period when in some instances, 24 or 48 hours may be sufficient. That is my question to the mover of the motion. We cannot, at the start of a session, predetermine a course of action for the coming year.