I can be extremely bored at a 3min video or totally immersed in a 10min video.
I can't watch longer ones, they're too boring usually.
There are a few exceptions though, for example "What the Cut 37" is a french show that is 42min long but entertaining enough so I keep laughing at every single minute of it. But that kind of content takes months to be created?
TL;LR: Keep it under 5 min.