I make videos playing traditional fiddle tunes. I try to keep the videos around 2:00 to 2:30 minutes long. Most of my videos are shot in one take with just a tripod, and people tend to get bored after about 2 minutes and no screen changes. If I had the energy, I'd edit different clips together to make things more interesting, but that's usually too much work for me to try to do for every video.
Once I get a higher engagement and more subscribers then I would feel more comfortable uploading longer videos.