Flash memory allows a limited number of erase cycles on a flash block before the block will fail. This number can be as low as 100,000. ETFS tracks the number of erases on each block. When selecting a block to use, ETFS attempts to spread the erase cycles evenly over the device, dramatically increasing its life. The difference can be extreme: from usage scenarios of failure within a few days without wear-leveling to over 40 years with wear-leveling.