It's not the nerves for me...it's the stomach. More than a couple of cups and it doesn't sit well.
On rare occasions I will have an afternoon or evening cup.
I have one double espresso a day, my wife gets up and brings it up to bed for me every day.
The training took some time but has eventually paid off.
I don't handle caffeine well, any more than that and I get the shakes and irritable. I sometimes risk a second one at weekends when I'm feeling brave.
On a serious note I have a real coffee obsession, I have a home roaster, huge cafe grade grinder and single group head espresso machine, along with a hand lever machine and pretty much every other method of coffee making you can think of down to an Ibrik.
I have a cup 1st thing in the morning and another around mid morning. I usually don't eat breakfast so more than 2 cups it bothers my stomach. After lunch I'm not in the mood for coffee any longer so I'd say my last cup finishes by noon at the latest.
Not a coffee drinker . . . but I find my sleep pattern is much improved since I stopped drinking tea after 6:00 p.m. Now, my "cup" of tea is about 20-26 oz.
I work in shifts, so it all depends on when I plan to go to sleep, but I try not to drink any coffee if I've past T minus 4 or 5 hours before bedtime. And anytime I have the option of decaf, I go for that after my initial morning cup or two.
Decaf is not a common option in Japan, so when I want it, I have to brew and bring it from home. I sometimes brew half / half, regular / decaf coffee and take that in a Thermos for later in the day.
I used to take about 5-7 espresso a day during my time in a Swiss engineering consultancy. The Jura semi-automatic espresso machine actually has a counter/odometer and the tech logs how many cups between the service. Divide that number to the number of staff, minus the non-drinker and I am about the average at 6-7 cups a day.
Right now, I am way down on my count. I take one early in the morning 0730 and perhaps 1 more after lunch at 1330. I can drink it late at night and still sleeps like a baby.