Caffeine half-life

Caffeine has a half-life of three to five hours. The best coffee regimen to maintain a consistent amount of caffeine in your system throughout the working day would be one cup of coffee in the morning—however much is required to feel alert—then a half cup every three to five hours throughout the rest of the day.

My current working routine is 60ml at seven in the morning, followed by 30ml at eleven, (four hours later) and then 30ml at three in the afternoon. Then by eleven-o-clock at night eight hours will have passed, and if we assume that caffeine in my system has a half-life of four hours, I will only have 15ml of caffeine in my system.