People like to talk about web video length as if it's a science. They are certain that your video should never be more than three minutes (or one minute, or twelve seconds) if you want people to watch from start to finish. And while there are a lot of practical reasons to keep web videos short, there's no pre-determined length that's ideal for all videos.
In fact, with higher-speed internet connections, HD streaming and full-screen video players, it's becoming easier and easier to upload and watch longer videos on the web. So don't listen to the know-it-alls who say your video will fail if it exceeds a certain length. Instead, think about your content, your audience and your video hosting capabilities to determine the ideal length for your web videos.