Yeah, I get the headaches that feel like migraines. But three days is about it. Then I felt pretty good, except I kept looking for something else hot and rich to have for an early morning drink, and the only thing that I found that really fit what I wanted was bone broth. But when I'm fasting, I can't have bone broth. Teas are too weak, water is fine but it's no replacement for coffee.
I've quit coffee several times for long periods. Usually I do it because I get tired of having a headache if I can't have coffee for some reason.