Carbide diff balls will last longer under the same circumstances as regular diff balls. If you are a 'backyard basher' or casual hobbyist who doesn't race, you should give your shocks a look over before each time you run the car. If you see any leaks, you need to rebuild your shocks. When rebuilding shocks, you should always use brand new o-rings. Racers should check their shocks before and after each run.
Any leaks mean it's time for a rebuild.
Either write it on the shock cap in a fine-point permanent marker or use one of the HPI Setup Sheets. When rebuilding shocks, you should always use brand new o-rings. Whether you race indoors or outdoors, you should check the teeth of each pulley before the day's racing begins for any rocks, tire debris, tape, etc., that get stuck in there. Drive Belts - Provide a way for power to be transferred from the gear shafts to the diff pulleys. Also, if the belt gets so loose that no amount of tensioning helps, you should replace the belt.