Pretty sure there's some age related effects too. Over the last ~20 years I've gone from being happily able to drink coffee after dinner, through not being able to drink it after 5pm or so, and now to having the espresso machine automatically shut off at 2:30pm - otherwise my sleep quality plummets.
I'm 57 now, I started noticing poor sleep related to late night coffee in my mid 30s. I do got fairly hard earlier in the day though, I've usually had 4 double espressos (somewhere between 17-21g of beans) by mid morning, and usually another one or two before my current self imposed 2:30pm cut off.
It's so funny but encouraging to read this. I started drinking coffee in college and could easily finish a whole pot, or have 3 Starbucks venti drip coffees in a day, but I was not sensitive to caffeine at all and could sleep right after. It also didn't seem to have that wake-up alertness effect either
Then something changed, and now I am sensitive to it like a normal person. It does wake me up after a sip or two I can feel it, and I can easily have 'too much' if I have 2-3 cups in too short of a timespan, so I've had to learn to slow down.
Having said all of this, my personal 'last call' is 6pm, with the idea that I will be able to sleep at 12-1am. But if I drink coffee after 6pm I might be delaying that bedtime a little.
It will be interesting to learn more about the effects of how much, and how long. Should I be tapering off hours before 'last call'? What is the best 'last call' time in the day and should it be earlier? I'll have to track some of this and figure this out!
My problem isn't falling asleep, it's staying asleep. Restlessness at night has become more noticeable as I've gotten older. Cutting down on caffeine, especially later in the day, seems to have helped some. I now have one cup of coffee in the morning, and a cup or two of tea in the early afternoon. This is instead of the two cups in the morning and espresso in the afternoon that I used to have before.
Everyone is different, but if you aren't already, and have the time for it, try incorporating more physical exercise into your day. That helped me deal with restlessness at night
For me personally, exercising makes me wake up multiple times at night and makes it hard to go back to sleep. I already never exercise after 6:00pm, it still happens. Any thoughts why?
Update: did a quick search, Reddit says it could be overtraining or dehydration.
Yeah it's well known that liver enzyme efficiency declines slightly with age. Also you may unknowingly run into medications that inhibit it, which gets more likely as you age and accumulate chronic issues requiring medication.
I'm envious of your 100 grams of beans a day consumption - if I have more than about 10g / one single espresso I'm a wreck for the entire day! The area-under-curve for slow metabolizers is 9 times larger - 3x the duration, 3x the concentration.
Honestly, I've noticed how sensitive I am to caffeine when I have reduced my caffeine intake. I think that it is important to clean the body before starting to observe, understand, and make conclusions about how a particular thing affects the body. Let it be caffeine, alcohol, or anything else.
I'm 57 now, I started noticing poor sleep related to late night coffee in my mid 30s. I do got fairly hard earlier in the day though, I've usually had 4 double espressos (somewhere between 17-21g of beans) by mid morning, and usually another one or two before my current self imposed 2:30pm cut off.