Demonstrating products for Ecommerce websites or Facebook or even Amazon takes creativity and a marketing sense to understand what will sell the product. It is important to display the product in the right context. All product videos should show either in use or a use environment. As far as timing goes, a product video can be both short and long form. Advertising videos with products tend to be short, unless you are going for an informercial style long form video. There are also informercial length, entertaining funny videos that demonstrate the benefits and value of the product, while entertaining the audience.
Sometimes product videos are how to videos. How to use the product, or how to set up the product.
On one hand you are marketing a product to an audience that is purchasing the product, but your audience might not be the ones that use the product. For example, Diapers.
Product Videos Increase Conversions
Conversion rates for product purchases increase 60% or higher when a visitor watches the product video. While you could add more copy to explain your product, humans process information both auditorily as well as visually.
Therefore, since the auditory stimulus reaches the cortex faster than the visual stimulus, the auditory reaction time is faster than the visual reaction time.