Rosabeth Moss Kanter writes in the Harvard Business Review that you can’t say or send a message once and assume that people have heard it:
Use the principle of redundancy. If the message is very important, send it through multiple media, in various forms, and do it a few times…even if people hear something once, they don’t necessarily remember that they did. Busy people with multiple projects might forget that something has already been discussed and raise it again at a meeting.
I don’t think redundancy is waste; I think it provides focus. If you want everyone to be on the same page, put the page in front of them conveniently and often.