Well, I'm Argentinian, and we here drink mate, which is another hot infusion with caffeine, that you take in small doses. It has less caffeine than a coffee, but it has. I drink mates every single day, in the morning and afternoons,and there are times when I doubt want to have that flavor, but then start feeling like I really really want to drink. I tried to quit and it was hard, I think I'm addicted. Every time I quit, I sleep much better at night, fell asleep instantly. When I make a trip, I don't consume caffeine at all, and I feel the same, sleep better at night, but after a week or so I start missing mate a lot, to the point that I want to come back to Argentina, and it's the first thing I do when I arrive... Never had a headache though, fortunately.