I find that Cory’s main points are spot on and include what caused me to move to a single monitor. When I was hired here at Don’t Panic Labs, I was running two 24″ monitors and my laptop on the side. Whenever I received a notification, I would see it in my peripheral vision. Sometimes that little split second of glancing over would cause me to lose my place in my code. I would then try to remember what I was in the middle of doing.
After dealing with these distractions for I while, I grabbed a spare 27″ monitor we had laying around and began using it instead of two smaller monitors. I loved it! The same reason why Cory uses a 24″ 4K monitor is the same reason why I use a single 27″ monitor. I think any size bigger would cause me the same distractions I just got rid of.
While I do have a 27″ monitor, I keep my laptop open on the side (and 95% of the time it is just displaying my desktop background). I find myself only putting applications on that screen to that do not need immediate attention and doesn’t have any type of animations that would catch my eye.
If you find yourself constantly glancing over to your other monitors without a purpose in productivity, I strongly suggest you consider using a single, larger monitor.