It's very interesting once you experiment with it. I had a much easier time fasting between 8pm -> 5pm, then from 8pm to noon.
Our bodies are so absurdly adaptive to just about anything we can throw at them. And so it makes sense, in some weird way, that if you're going to do something - doing it to an extreme degree can make things easier than going half way, since you optimize for the adaptive response from your body.