Mastiffs are known for their long life expectancy, with most living up to 10-12 years. However, some breeds may live longer due to their size and genetics. Bullmastiffs can live up to 12-13 years, while Neapolitan Mastiffs have been known to reach 14 or 15 years old! Tibetan Mastiffs tend towards the shorter end of that spectrum at 8-10 years but still provide many wonderful companionship moments.