Fortunately I have a natural dislike of looking at a screen for longer than 20 minutes, or even sitting at my computer for that long, and I get up, move around, and do something else, for much longer than 20 seconds. But then I am retired and do not earn my living at a screen, so that is easy for me. What I look at over the top of my smallish screen is also further away than 6 m - 8m to the French windows and 65 km or more to the mountains I can see through them, with plenty of other distances in between. This is the advantage of living in a converted barn in the middle of the countryside.
Even looking up at my ceiling when lying on my sofa gives me a good distance. That brush against the wall, used for getting rid of spider webs, has a handle 4 metres long. The apex of the ceiling is 5.5 metres. Alas, I now see the spider webs more often than I used to.