Variation is the result of change, either known (ink key adjustments) or unknown. Variation is the opposite of consistency or stability. All should define a duration or period between sheets. A common interval is every 500 shts. Any press stoppage will immediately cause color variation since the delicate lithographic balance between ink & water has been disrupted by a disturbance. The closer your first makeready (MR) pull (sample/measurement) is to the target aim, the less time, sheets, effort, money is needed to get to the desired target aim. This is why CIP3-4 prepress ink key presets and a calibrated press-to-proof are so important. I think many older technology 40" sheetfed presses can achieve a color OK (close/good enough commercially acceptable color match) after 2 pulls of 200 sheets each.
Do you stop/restart the press between MR pulls or does your MR run steady at run speed and you get the OK on the fly?
Regardless of the technology and process, most decisions are ultimately a business/financial/productivity one, hopefully quality too.
It often comes down to a compromise or tradeoff between quality and cost. A closer match will need more time and paper which costs more. Was it estimated for, will the customer/market pay for it, am I making enough profit?
