From my perspective, I used to get headaches playing Doom on a 15” CRT, but I figured I was just getting too old (and haven’t gotten any younger in the 30 years since). If you can do intense gaming a whole weekend on one or two 27” screens without a headache, you are doing well!I tried it once by using a 43" TV on my desk for 4K gaming.. it was an amazing experience.. but I started getting headaches after a couple of weekends of intense gaming. So I got rid of that screen and use my 2nd 27" Monitor now.