Depends on the "author." Most tree work videos I won't watch, short or long, because I feel like I know the game and plus I have my own creating to do. So I guess as a viewer I have to vote 5-10. . . or less even. People often ask me to watch their videos, but I can rarely finish them due to monotonous or clunky content/work or editing style. I catch all Reg's vids because I like him and his style and I identify with his content or find humor even if I might disagree with a detail and not get to hating Starbucks so much as he does.
Plus he doesn't make a ton of videos.
As a creator myself, I just do what I want and make them for myself. I enjoy making them and make many for the family that don't make it public. Like I've said before if I didn't make them for fun I wouldn't make very many. I do what I want.
If someone finds they're too long for one sitting I assume they can come back to it. After all, if you click away, YouTube holds your place in the video.
I ponder formulas for getting more views (short length, catchy titles, etc.) but at the same time I abhor views as a motive and the whole click-bate bs I see so much.
Everybody is somebody else's weirdo so I can't make em all happy anyway.
I may as well do what I want.