I think it is roughly the same time every day, but C-Span does not show it live very often because they have to show the Bloviators on the Hill if they are in. Generally you can watch it on the White House web site, but it's not often up until early evening. Transcript comes out first.
Thanks, that's very helpful! I've never had any interest in watching the briefing before, but I can't wait to see Tony in action.