No one wants to watch a long, boring video. Keep things short and sweet - try to keep videos no longer than 2 minutes if possible. That way, viewers will be more likely to watch until the end and not get distracted by other things on their screens.
If you have a lot of information that needs to be conveyed in one video, consider breaking up the content into multiple shorter clips instead of one long one. This will help keep viewers engaged without overwhelming them with too much information at once.