She’s been drinking a mug of black coffee with me in the mornings occasionally. I have a drip maker that I put 4 teaspoons Maxwell House in. Nothing beyond that.
I got this message around 11AM. We drank the coffee around 715-730.
I get that I wasn’t exactly the most sensitive I could have been, but I’m a rural mail carrier. I had to respond while stopped at a mailbox and we are GPS tracked. I get in trouble if I spend too much time stopped.
It’s a range, but lots of things can increase the half life, from being pregnant to oral contraceptives, and there is a difference in rate of reported effects between men and women. One source.
Most importantly, there is a massive variation in how sensitive individual people are to caffeine.