At least that's whay my Doc told me last time I saw him. Noodling around online, it seems that the half-life of caffeine can vary anywhere from 2-3 hours to 10

At least that's whay my Doc told me last time I saw him. Noodling around online, it seems that the half-life of caffeine can vary anywhere from 2-3 hours to 100 hours depending on the person, their metabolism and if they smoke or not.