Well I think the key point is that caffeine has a half life of 6 or 7 hours in adults. So 4 coffees before 10am is worse than one coffee at 2pm. That's how I look at it anyway. Regardless, I limit myself to 2 cups before 8am. Now I notice even a late afternoon green tea wrecking my sleep. Can't believe I spent all those years drinking 5 cups well into the afternoon...