Eli5 why can’t we continuously take caffeine and never sleep?

Question

I work overnight shifts (11pm-7am) and take caffeine pills to stay awake. When I get home, even if I take more caffeine I’m sometimes still too tired and fall asleep. Why does it eventually stop working? Is there some sort of chemical limit? Why can’t caffeine replace sleep for longer periods of time (like days on end)?

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Answer 1

The WIRED “support” episode about sleep covers this. Take a peak if you want.