What is the ideal length for a video advertisement?

According to Visible Measures, your video only has 10 seconds to grab the attention of the viewer, because 20% will click away within ten seconds or less. In Mission Impossible terms, your video self-destructed right about then. 

The statistics don't get much better, as one third will have left by 30 seconds, 45% will have bailed at 1 minute, and by 2 minutes, nearly 60% are done and out. 

Which is why writing and producing a video that delivers the pay dirt takes a lot of skill. Anyone can write. And ramble. Only those who hone their scriptwriting skills every day will make each word carry the weight of a sentence, and condense a paragraph into a one-liner. Mark Twain famously said, "I didn't have time to write you a short letter, so I wrote you a long one instead." 

So do your brand and your audience a favour: have your videos produced by those who won't write you a long letter.