People have been discussing issues like this since there have been e-ink screens and it's always been the same. Some people are just fine reading an LCD screen and have no issues at all. Others can do it if they adjust various things. And others have to limit their contiguous reading time on backlit screens.
I'm in the latter group and I've done a lot of experimenting over the years and found what works best for me. I adjust the backlight so it's as dim as it can be so I can read comfortably. I use a sepia background. I can read a bit longer if I reverse the text but I don't enjoy that so I rarely do it. I prefer to take breaks.
If I take a minute or two break every 15 or 20 minutes on an LCD screen I can read as much as I want. On my phone with it's OLED screen I can read 25 or 30 minutes and take a break for a minute or two. On both if I don't take that break I'm soon unable to read for a few hours.
In the past I could read as long as I like on my Kindle. In recent years that's changed and I have to take a break about every hour. Given my reading habits these days all of these methods work well for me. At home I use my Kindle and I rarely read more than an hour. If I do I just need a short break and (I'm 78) I have to take enough bathroom breaks that that's nearly automatic.
Away from home I read on my phone while waiting in the doctor's office or in line at the grocery store, etc. It's unusual to have a chance to read more than 20 or so minutes then.
In my younger days I would sometimes read from the time I got up to the time I went to bed. It almost never bothered me. I'd walk to the park and sit under a tree on a summer day and read till i was hungry. I'm pretty sure that picture on the Kindle start up screen was inspired by me.
If you can read all day I'm happy for you. i wish I still could. But I can read enough that I'm okay.
A few years ago there was a woman in my retirement home who loved to read. She would come to the community room and sit and read and drink coffee and spend hours every day. Then when she began to lose her vision I helped her get going with audiobooks. She was doing that when she moved out into a nursing home. About 2 years ago her daughter brought her here to visit and she'd lost her hearing and we spent a few days looking for a way for her to peruse books but nothing we tried worked. I recommended going to a city that has a lighthouse for the blind to seek help but she was too discouraged to try it.
Barry