The consumable items on the LongMill are the v-wheels and the delrin anti-backlash nuts.
We recommend replacing your v-wheels every 1500 to 2000 hours, or when the v-wheels have worn down to the level where the eccentric nuts no longer provide any tension. You can tell if they need replacing if the gantries are loose on the rails even after adjusting the eccentric nuts to their extreme position.
We recommend replacing your delrin anti-backlash nuts every 1500 to 2000 hours, or when the tensioning screw does not allow for any more adjustment.
More information on machine maintenance can be found here.