Let me start by saying that the optics are important, but not out past 400 yards the most important thing is who you steady it. Probably not even past 200 to 300 yards. At just about any long range distance, you will need some form of monopole or tripod to hold the range finder rock steady so that its target will not be dancing all over the place.
Most ranger finders we use are used for relatively short distances (<200 yards), where you can keep the target (cross hairs) relatively in the same place. When we try to stretch the distance a bit, I always take a tripod.
I have shot at targets 400 yards a way with iron sights and I could hardly see the bulls-eye. Magnification and quality of optical sights is absolutely critical at any real distance. That means it is not so much the quality of the laser chip (there are probably only a few rangefinder chip mfg’s) but the quality of the optics and the magnification power are what will make a difference in how well you can use a range finder at distance.
Personally, I don't feel shooting at anything beyond about 200 yards is warranted. If it is at 400 yards, it means you just need to get closer to what it is that you want to shoot.
i think you have to consider something at 400 yards possibly coming towards you at a variety of speeds and reasons.
One time I was shooting with my Nephew. The rifle was a 98-09 Argentine Mauser in 7.65X55 Mauser. It was a very uncommon rifle for both the workmanship and the fact that it came with it’s original test target in which Herr Ritzman had fired a sub 2 inch, 3 shot group at 200 meters. The bullets were striking about 2 inches above the aiming point.
My Nephew found an old roofers tar bucket about half or two thirds full of tar. We sat it out at a measured 400 meters. We used a car odometer to measure the distance so not exact but still pretty close.
It turned out the rifles iron sights were dead on at 400 yards so we had to make no adjustments. I believe I hit it every single time using the roof of a car as a rest. What really surprised me is my Nephew who is not a particularly good shot, hit the bucket more times than not from a standing position. When it was hit the bucket would move, sometimes more other times less.
That is the reason I decided 400 yards was not really hard.
I later fired at an old syrup cooker from ranges greater than that, then much greater than 400 yards. Accuracy dropped way off. We could hit it about half the time but we are talking about something maybe 8 ft. by 3 ft. Every hit made a loud clang on the cast iron.
At 400 I was confident. At 600 not confident at all.