Its been about 4 years now. About 2 ounces of most black coffee in about 5-10 mins is enough to really feel it. If I ever have a tea or coffee I have about 8 oz over about 6 hours usually. I used to be a 2-3 coffee/energy drink person, for about 6 years prior. I have gotten used to coffee/tea at room-temp believe it or not, and I'm not that guy, that likes room temp drinks. Insulated cup helps a ton!

On a second note, I had a goal to drop all substance "addiction" basically anything I ate/drank that I felt dependent on for my productivity or mood regardless of how long it took. Generally eating better, sleeping better, and working out daily, has done so much more for my productivity than any cup of coffee has or will ever do for me. When I know I have a large block of time I can use to focus on a single task, I will sometimes have a couple OZ of coffee or so. The last thing I'm working on is sugar...