The bull market turned four Saturday. But no bull lives forever. The average lifespan of a bull is 4 years and 8 months. That short average lifespan is why Wall Street is checking the bull's vital signs.he 2002-2007 bull lasted five years. The decade-long bull that ended in March 2000, the longest bull in history, lasted 113 months, or more than nine years. It was also the biggest-gainer of all-time, posting a return of 417%, more than double the 162% average gain since 1932.