We agree on the 10- minute rule. If we want to have some time left, we need to arrange not to hear from 20 witnesses, each of whom would have 10 minutes. There wouldn't be any time left to ask questions. In short, we will need to manage our time according to the number of witnesses scheduled to appear at each meeting.
In any event, out of consideration for the witnesses, we need to allocate a minimum of 10 minutes to each individual. Witnesses will have the chance to respond and to clarify their comments if members confine themselves to asking more direct questions.