The velocity of a printhead scanning across a sheet of paper or other print medium is varied on the basis of whether masking patterns for selectively activating nozzle of the printhead include activations in consecutive pixel locations of the masking pattern. The pixel locations are “firing opportunities” as defined by the maximum firing frequency assigned to the nozzles when the printhead is scanned at a particular velocity. The printhead is moved at that velocity when a masking pattern includes activation in consecutive pixel locations. On the other hand, a higher scanning velocity is available when a constraint is enforced to prevent occasions of firings in consecutive pixel locations. In one embodiment, the constraint is not enforced, but masking patterns are analyzed on a pattern-by-pattern basis to detect those patterns which satisfy the constraint, so that the scanning velocity can be increased during the suitable masking patterns.