A printing system includes a plurality of marking engines. The marking engines selectively receive at least one replacement module, such as a toner or ink cartridge. The replacement module includes a consumable such as toner or ink, which is consumed during rendering of images by the respective marking engine. A scheduling system assigns images to the marking engines for rendering on a print medium, such as paper. The scheduling system has a mode of operation in which images are selectively assigned to the marking engines to balance usage of the consumable by the marking engines.