“No one ever complains about a speech being too short!”    – Ira Hayes
There are lots of quotes that convey the same sentiment – e.g. “always leave them wanting more” – and for good reason. You can never really be too brief, but you surely can be too long-winded.
So the tip of the month is to err on the side of brevity. Even the best speakers can lose their audiences when they overstay their welcome.

You’ll never be criticized for being brief; you’ll probably be thanked for allowing the audience time to ask for the detail they’re interested in hearing! 
It is, after all, all about them!
Beth Levine