Nobody important has time to read or listen to someone droning on and on about something. If you can't get your point across succinctly and clearly, you need to work on your communications skills. You shouldn't be saying anything that doesn't need to be said.

Be brief and poignant and you can come off well-spoken and interesting. Think about the people you know in your life who love to talk and talk... How interested are you in what they have to say?

I'd say when describing many ideas/concepts, being more complete is okay, but unless you are an amazing story-teller, keep it interesting and to the point.

Plus... the Spartans loved being brief.