As for performance based on the length of a video ad, there was considerable variation and lack of a clear trend line. Completion rates were lowest for video ads that lasted between 30 to 60 seconds (77%), but ads that ran for 30 seconds or less saw an 84% completion rate, the second-highest of any video ad length measured, indicating that short ads do not necessarily equal low completion rates. The absolute highest completion rate went to ads that were between 30 and 60 minutes.
Most likely, very few ads actually are as long as 30 minutes, or even 5 minutes, which may mean that viewers who sign on for such video ads are particularly receptive to them. But the other takeaway is that how compelling the ad is may be more important than how long it is. Read the rest at eMarketer.