The "wear" in a shock mainly takes place at the piston seals and rod seals. Changing your shock settings between Comfort, Normal, and Race modes alters the amount/time of the oil flow between the chambers within the shock, and thus the speed at which the components move against each other. Running in Race mode slows down the speed of the piston within the shock cylinder (as well as the rod through its seal) due to the increased viscous drag and thus should reduce the wear rate within the shock, though the associated bushings on the shock and other suspension components will wear more quickly, as they will be exposed to greater loads on each impact. Whether or not this reduction in piston speed will make any sort of tangible difference in the lifetime of our shocks is beyond me.