It's convinced me that my nearsightedness has come about due to the nights I spent reading books by the light of the streetlight outside my bedroom or a torch when I was a kid (after I was supposed to have gone to bed).

So IMO, what you really want to do is to avoid sitting in a dark room with a bright screen glaring in your face or straining to watch long movies and binge watching TV on your tiny 6 inch phone screen or read books without the aid of at least a lamp next to you. In general, use common sense and don't take things to the extreme. Anything that accelerates fatiguing the eyes should be avoided. That's not to say don't sit in front of a screen all day; that's pretty much all I do, but in a well lit room and with regular breaks my eyes never experience fatigue. Also, as someone else posted, having the right prescription for your glasses is also important.