How long does caffeine last?

Question

How long do the effects of caffeine last if I rarely use it (eg. usually only about once or twice per year)? For example, if I take about 12mg of caffeine (typical in a can of cola), how long should I expect to stay alert? How does the effect increase as I take more , as in 35mg in a cup of coffee?

Answer 1

I doubt if you'd even notice it if you weren't aware and expecting something..