I hear this question frequently. In fact, I was interviewed by WNAV-AM 1430 news talk radio in Baltimore this morning. The question about timing came up there as well.When it comes to creating a speech, less is more. The audience will actually remember more of a shorter, more concise speech.
The ability to get your point across clearly, concisely, and quickly is an advantage for any speaker. I tell my audience to always have a short version of their speech. If you have a one hour presentation, be sure you can deliver a 10 minute version. If your time is cut short, you'll still be able to deliver a powerful message.
Watch how Steve Jobs cut a 90 minute keynote into a 60 second speech. Do you remember the points? You bet.