Have a look here.
A flash device that is rated at 100,000 write cycles, for example, can write 100,000 times "to every single (memory) cell within the device. In other words, the device doesn't write to the same cell over and over again but spreads out the writes over many different cells. This is achieved through "wear leveling," which is carried out by the SSD's controller.
This would make it virtually impossible to wear out a flash chip