3 cups of espresso would be a fantastic amount of coffee. You'd actually have a medical condition of you drank that much espresso every day:

~64 mg caffeine / ounce in espresso

64 mg/ounce * 8 ounces * 3 = 1536 mg

From wikipedia: "Consumption of 1000–1500 mg per day is associated with a condition known as caffeinism."