[Pseudoscience-is-malarkey (OP)]

Is soaking coffee grounds longer really the best way to get as much caffeine as possible? I was young when my grandfather went to his grave, but I do recall him using a percolator for his coffee and resting the grounds in it for a little bit longer than my mother or whoever. During the war, he flew such long missions in the pacific and he and his flight would do that practice he once explained to me. It worked in the war, and apparently, it worked in peacetime, especially during his long hours at the funeral home.

I also once asked him why puts a little bit of ketchup on his eggs. "During both the Depression and the war, that was the cheap condiment we could afford".

[evan_au]

Soaking the grounds longer will get out more caffeine. But it will also leach out more chemicals too, which might make the coffee more bitter. To each his own...

[Bored chemist]

Soaking the grounds longer will get out more caffeine. But it will also leach out more chemicals too, which might make the coffee more bitter. To each his own...

It turns out that coffee is made entirely from chemicals. Some of them, like caffeine, are bitter.

There's a limit to how good a job you can do with soaking (unless you keep changing the water),  but in principle, a percolator will leach out all the caffeine if given time.
If you were doing it in a lab, you would use one of these
https://en.wikipedia.org/wiki/Soxhlet_extractor
I sometimes wonder if you could sell one as an "executive toy".