5/10 interestingness gets 0 seconds of watch time for me, there's just too much quality content produced in my topics of interest every day for me to keep up with. I already have to miss some 7/10 projects just because there's only so much free time in a day.

Regarding the time question, for something that barely crosses the "okay I'll watch it" threshold, 10-15 minutes is probably what I'll give it. It can be longer than that, I'll just skip through parts of the video for the gist to decide if I want to give it more time.

Worth noting though, that for extremely interesting content, a 15 minute duration actually dissuades me from watching it, as I doubt there's enough time to cover much of anything at a decent level in that little an amount of time. So like, for a neat history vid on a topic I'd like to hear more about, if it's 30 minutes or less then I'm less likely to give it a chance, unless it's covering something super narrow where there wouldn't be as much to talk about. But if you're going to cover a major historical event, you better be at least a half hour. There are some exceptions to this, Indy Nidell(sp?) is a good example, but it's my general rule.