The tyranny of afternoon coffee

Both Mary and I have gotten in the habit of drinking a little coffee in the middle of the afternoon. Which is great, so long as we don't go too late.  The problem is that figuring how to space out lunch, exercise, and other stuff we need to do gets complicated, because we don't want to push the coffee back too late in the day, lest it mess with our sleep schedules, which are themselves rather imperfect.

I am well aware that this is not the greatest of habits, that many fault caffeine as being one of the great crazymakers of modernity.  I know, I know.