Approximately 1 second was how long AI could hold it together. If you had a lot of free time you could extend that out a bit, but it'll mess something up. So generally people who make them will run it slow-motion. This is the first clip I've seen with it at full speed.

The quick cuts thing is a huge turnoff so if they have a 15 second clip later on, I missed it.

When I say "1second" I mean that's what I was doing with automatic1111 a couple years ago. And every video I've seen is the same 30-60 generated frames...