Because copper optics for CO²-ICF system applications will be highly stressed, the single-shot damage thresholds which have been reported [1,2], provide only part of the information needed for accurate performance predictions. We report here a performance comparison for copper mirrors finished by different techniques, including single-point diamond turning (SPDT), showing for the first time the relative decrease in 10-μm damage thresholds corresponding to multiple shots, and the loss of reflected beam brightness arising at high fluence levels. We also report the intensity and energy loss due to plasma formation when Cu mirrors are used in air.