Your eyes make no distinction though. Make sure you're resting them 20 min of every hour. Take it from a guy who's been doing this for decades and didn't do that when he was young.Thing is, I think there are two categories of screen time; productive, and wasted. I spend a lot of time messing around with my various computers, working on projects and whatnot. That could easily be a few hours. Same for ebooks. That's productive, as I'm feeding my brain. Whereas if I sit here on BYC or scroll Reddit while not doing anything that gains me benefit, that's wasted screen time.