how long does caffeine stay in your system?
<answer> The half-life for caffeine is anywhere from 4 to 6 hours on average. <context> Advertisement. It only takes 45 minutes for 99% of the caffeine to be absorbed through these membranes. In humans the half-life for caffeine is anywhere from 4 to 6 hours on average, which explains why the average energy drink or coffee’s effect lasts about 4 to 6 hours.dvertisement. It only takes 45 minutes for 99% of the caffeine to be absorbed through these membranes. In humans the half-life for caffeine is anywhere from 4 to 6 hours on average, which explains why the average energy drink or coffee’s effect lasts about 4 to 6 hours.