This should be a more official recommendation somewhere. It also lives on Office wiki, but it should belong to TCG. Just like there are no rollouts on Fridays, there should be no (major) announcements on that same day as well, in particular if the announcement is deemed to be potentially troubling and may cause immediate and worried reactions, it is important that the entire team (not just the CLs) is around to address questions promptly and to help achieving a well informed and balanced conversation.
