You could wait until you’ve cranked the turrets up towards 6 mil or so. But you might as well every shot. You’ll get some drift once you start dialing a lot if you don’t readjust parallax once you’ve cranked enough.
But, you’re checking to make sure your precision instrument does exactly what it’s supposed to. So why not check your cant and parallax at every mil, so that you can rule out as many error factors as possible.
Info is straight from vortex amg dept when I had a conversation with them on testing my AMG.
So when I plug in your environmentals Rob01 it shows what you're seeing. Just in case anyone is wondering, at 300 yards this is how much each field changes the elevation. The first numbers are what I had, the second ones are Rob's.
Sight Height - going from 1.8 to 2.0, dropped it 0.1mils
Pressure - going from 28.50 to 29.98, adds 0.2mils
Temp - going from 80 degrees to 60 degrees, adds 0.3mils
Elevation - going from 1850 to 350 feet, adds 0.2mils
Humidity - 0 to 50% adds 0.2 inches of drop, no difference (changing it to 100% changes it 0.4 inches so you can just ignore humidity)
So changing those 4 things made a 0.6mil difference, an additional 7.1" of drop.