I often drink too much coffee so I try to keep to just one cup of coffee a day. I suppose many people drink too much coffee at work as well.
Because of the effects of caffeine, you can probably concentrate well and better deal with sleepiness after having some coffee. It also helps burn body fat too. Due to its stimulatory effect, coffee seems to have originally been drunk as a form of medicine.
The caffeine in coffee is absorbed into the brain in approximately 30 minutes, and it has a half-life of 3-7 hours (that is, it takes 3-7 hours for the level in our body to be reduced by 50%). However, the stimulatory effect can’t be increased even by drinking coffee twice or more during that time. On the contrary, tolerance to the effects of caffeine builds up if you drink too much, and you should be careful not to have too much coffee as it may cause a headache. So be careful and just enjoy your coffee!