I've also been buying a larger monitor every few years, as the prices drop.

But I hated the 42" 4K I tried and returned it. The problem was the edges are just too far away. If I use them I end up with the same kind of neck strain I would get with a multi-monitor setup. So I only used kind of the middle section of the screen anyway. And at 42" 4K the physical pixels are just too big - everything is fuzzy.

32" 4K is the sweet spot for me. Maybe when there's a reasonably priced 42" 8K curved display I'll give it a go.

Do you know if your neck strain is due to horizontal or vertical movements? On a few times I had to work with big monitors (>30"), I noticed that I placed/sized windows only at the center, and not all the way to the top. Looking up too much is not comfortable for my neck. For the horizontal movement, I have no problem. But when my eyes are focused on the centre part, if I need to look at the extreme left/right, I need to refocus, which is slow/tiring.

My work setup is 2x24" monitors, and I really prefer 2 small ones instead of a bigger one. I can orient them so that all pixels are approximately at the same distance to my eyes.

The vertical was definitely more uncomfortable than horizontal.

Yes this. I have 20/20 vision but as I got older getting some mild reading glasses dramatically improved my development experience.