At what age do people actually figure out what 'resting your eyes' means?

Growing up, everyone has that moment where a parent is sitting dead upright on the couch in the middle of a loud room, sound asleep, but the millisecond you reach for the remote control to change the channel, they snap awake and say: "I was watching that, I'm just resting my eyes."

When does this evolutionary biological switch flip inside us? Because last Sunday afternoon, I sat on the carpet to pet the dog during a YouTube video, closed my eyes for "thirty seconds," and woke up four hours later with carpet pattern marks pressed deep into my cheek, completely unaware of what year it was.

Is there a formal initiation ceremony where you unlock the ability to fall asleep mid-sentence, or does your spine just decide it's done around age 22?