4 hours just staring at a watch?! That's ridicilous. I MAYBE use my phone that much on active days. Who has time?
You MISSED the point. The point is that it will last for 4 hours if the screen is CONSTANTLY on. The screen is only on when your wrist is raised so unless you plan on walking around with your wrist up looking like an idiot all day long then it will last for a lot longer than 4 hours, probably a day.