What is the ideal video length for facebook?

I had some insights about it thanks to our statistics but after reading a dozen of different articles/stat reports it appears that the best video length for FB is between 30 to 60 seconds in term of social engagement and overall watch time. Across all the stuff I've read here is a very well written article that gives you pretty much all these useful stats that might help if you market your products or brand on facebook:

For those who don't want to read, here are the stats for video consumption on facebook:

- 44% of 30- to 60-second video ads on Facebook were viewed to completion. Meanwhile, those that ran 30 seconds or less saw a 26% completion rate. Interestingly, 2-minute or longer video ads had the second-best completion rate of 31%.
- Facebook gets over 8 billion average daily video views.
- 85% of Facebook users watch videos with the sound off.
- People are 1.5 times more likely to watch video daily on a smartphone than on desktop.
- 47% of the value of Facebook video ads happens in the first three seconds.
- Millennials are 1.35 times more likely than older generations to say they find it easier to focus when watching videos on mobile.
- One in five Facebook videos is now a live broadcast.
- By 2020, over 75% of the world's mobile data traffic will be video.
- Videos earn the highest engagement rate, despite making up only 3% of content.
- 85% of Facebook videos are watched with the sound off.

Now let's try to put all this in practice and for that reason I thought that instead of making long  videos it'd be better to focus on short/qualitative content. What do you guys think?