If you have a page with a large following where people are actively seeking you out to consume your content, people with have much more patience. These are your organic posts, the ones that you publish in your feed.
In this case, people are invested in your content and you can produce longer form video to accommodate your communication goals. Facebook will allow you to post a video up to 240 minutes long. Hubspot found they got the most engagement from a one minute video.
Your consumer will still not cut you much slack. Facebook recommends that small businesses limit their videos to 15 seconds. Your customer will take just 3 seconds to decide whether to watch or not.
Optimise for mobile – 88% of people view their feed on their phones.
Optimise for no sound – 85% of people watch with the sound turned off.
Now, that is the recommendation for organic posts but they will not give you much reach unless you already have a large audience.
If you use video with your paid ads bear in mind, people are not invested in your content. You have to try harder. Get to the point quickly. Use copy to make your ads more effective.