Xerographic process controls scheduling approach to mitigate costs of measurement

A method and apparatus for maintaining color consistency includes varying a sampling interval to balance the benefit of xerographic process controls regulation with the cost of sampling. The request to sample is triggered by external indicators (area coverage, carrier age, relative humidity, temperature, etc.). Before the developed mass is expected to go out of range because of the external indicators, a patch measurement is made and the system is controlled back towards its desired set-point.