Obviously you missed out on the negative nootropic effects of caffeine.

Sustained caffeine intake will develop some form of dependence. Brain activity was shown to be reduced when someone takes caffeine everyday. This activity can be restored to 'normal' when caffeine is consumed. Hence, the slow sluggish feeling you have if you're a regular coffee drinker without your morning buzz.

A week or so without caffeine would reverse this dependence. It was a NatGeo article. I don't think you can develop tolerance to caffeine. Withdrawal effects are minor. The most significant effect of caffeine withdrawal is fatigue.

On the other hand, caffeine promotes short term memory but doesn't help with long term. So it's a good idea to take before your exams, but not a month before. Haha.