There are several factors that help determine the proper length of your video.
The 30 second commercial promotion has a very specific formula to grab the attention of a visitor to your website and engage them enough to read more. This is best for launching an offer or new product with a singular, focused value proposition.
The 60 second spot will be required to have enough compelling content to keep viewers beyond 30 seconds, which is a significant drop-off point. If you have ‘enough’ content to add value to the message, thereby increasing chances of conversion, 60 seconds is a safe video length to keep viewers on your site.
Product demonstration videos that are used as sales aids can arguably run much longer because you are providing very specific information that the viewers want to see. Combined with proper SEO, this can be the most powerful way to use video to increase sales.
Sales training videos would run the proper length to ensure maximum content recall and best integration with other learning aids.
Documentaries will need to be gauged for the amount of compelling, educational content.
Corporate videos will often be mandated to be watched their full length by all viewers. But keeping it short, or breaking up longer videos into shorter segments, ensures best information recall and engagement.
Finally, where you plan to distribute the video matters. Instagram, Facebook, and Twitter may not lend themselves to consuming longer videos. Few people on social media will immerse themselves in a long video unless, of course, the video has already gone viral or it comes highly recommended from your network contacts. Perhaps you are better advised to produce teaser videos for social networks that link back to your main site. This is a very simple, available service that we provide my clients if required.