To determine the average lifespan of any mixed breed, one should consider the dog's weight. Dogs over 90 pounds usually live for approximately eight years, while dogs under 90 pounds tend to live approximately 11 years, according to the "State of Pet Health 2013 Report" from Banfield Pet Hospital.

Mixed animals and female dogs typically live longer than purebred dogs, according to Steven N. Austad, PhD, a researcher and professor at the University of Texas Health Science Center in San Antonio. Purebred dogs, which are often subjected to inbreeding, frequently have health problems that are common among their particular breed.