There is no saying that British Shorthair cats will not live longer than five years old. Normally, the average life span of cats is about 12-15 years. Generally, domestic British Shorthair cats can live to be ten years old or even longer. Some cats may be If an accident such as illness occurs in the middle, you will die in a hurry. If the British Shorthair in the family dies normally after growing up to five years old, the biggest reason is due to incest.