All studies confirm that caffeine consumed regularly does not improve alertness or anything else above baseline. After a tolerance is built, daily caffeine only

All studies confirm that caffeine consumed regularly does not improve alertness or anything else above baseline. After a tolerance is built, daily caffeine only returns the user to baseline performance, that they have fallen under due to withdrawal. If you use caffeine for more than about 2 or 3 days in a row, it stops doing anything useful. If everyone quit caffeine immediately, there would be a couple weeks of awful productivity, and then everything would go back to normal.