Long time ago when I was chronically tired and with random sleeping patterns (going out, staying late...) I could drink strong coffee 30mins before sleep and have no problem getting to sleep. But some time later when I normalized with daily rhythm and stress I could not, I had to drink last coffee before 4pm, then a few years later before 2pm and less coffee. Now, when I am religious about getting to sleep before 11pm and am mindful about my energy levels, stress, eat well for long periods, train moderately, one coffee in the morning is more than enough to feel strong kick until the evening almost. I am thinking of even dropping that for some black/green tea. I think that so many people are chronically overstressed, undersleeped and with overworked adrenal glands, that they can’t even notice the real downside until they get into a better position for some time. And coffee in a run down body is just for keeping things bearly going.

I drink coffee/espressos each day, probably too much. Just recently after not having my usual Americanos I had a massive headache before bed. Advil did nothing so I figured it must be a caffeine withdrawal headache. They're hell and there's no way I can sleep with one so I made a shot of espresso and downed it quickly. Within 30 mins my headache went from a jackhammer pounding my skull to a distant woodpecker, and after another 30 mins I was asleep and slept fine. The big confounding factor with caffeine studies might be tolerance.