A moderate caffeine intake is considered to be 250 mg/day. In research studies, the amount of caffeine that enhances performance ranges from 1.5 to 4 mg/lb body weight (3 to 9 mg/kg) taken one hour before exercise. For a 150 lb person, this comes to about 225 to 600 mg.
Caffeine is susceptible to intolerance, which means the long-term effects will severely diminish in an insurmountable why; meaning increasing the dose won’t do anything. An effective method to counter this is cycling off caffeine for 3-7 days, every 1-2 months. *Depending on how much caffeine you consume daily, keep in mind some pre-workouts have extremely high amounts of caffeine in them.