[fultonfaknem42]

You could do the math if you look up the half-life of caffeine. Via a quick Google search it looks like it is 4-6 hours. So if I understand it correctly, it's 4-6 hours for 100mg to become 50mg, then another 4-6 for 50mg to become 25mg, etc. So like if all you did was have a single cup of 100mg coffee, then its like 12-18 hours for it to go away. If you're me though, you drink like 3-4 a day. This seems to be about 28 to 42 hours. Withdrawals could take up to 2 weeks in my experience, and are proportional to how heavy my intake was.

[samatman]

That tells you how long before it's out of your system, not how long it takes to reset after.

Effect duration for a psychoactive is related to half-life, but they aren't identical, and 'reset time' varies widely, e.g. MDMA is over in about 4 hours but it takes at minimum of two weeks before one can get a comparable effect again.

[hombre_fatal]

You'd have to look at things like the rate of downregulation of the appropriate brain components that caffeine affects.