Another N=1: I consistently need less sleep when I drink 1 dose of caffeine each day. I used to need 9 hours of sleep a night, now I'm no longer extraordinarily fatigued with 6-7 indefinitely.

I only came into my caffeine habit in my mid 30s, and the change was pretty dramatic and immediate.

Whether I'm slowly killing myself by not sleeping enough is another question entirely that I only wish I knew the answer to.