Theoretically, it can be preserved indefinitely. At present, the cells that have been frozen for the longest time can still be used normally for about 70 years, not because cells can only be preserved for about 70 years, but because the technology of freezing cells has been invented for more than 70 years. With the development of the times, the period of cryopreservation of stem cells will continue to extend. The cells were stored in the gas-phase liquid nitrogen tank of Huaxia SNC Life Bank-196℃.