Full tolerance develops with prolonged and repeated use
Between uses, it's recommended to wait:
At least 3 - 7 days
Ideally 1 - 2 weeks
Toxicity
The LD50 of caffeine in humans is dependent on individual sensitivity, but is estimated to be about 150 to 200 milligrams per kilogram of body mass or roughly 80 to 100 cups of coffee for an average adult
Addiction potential
Produces dependence with chronic use and has a low abuse potential