The key factors that determine how long a dog will live are:
Size of dog.
Generally, small dogs live much longer than large dogs.
NOTE! IN the first year of life they reach mid teen….wow! AND by the second year of life already in their 20’s…fast growing.
The breed of dog is a strong indicator of its life expectancy. For example, a Doberman Pinscher can easily reach 15 years of age despite the fact that it is a large dog (about 35 kg.) whereas the smaller Boxer is shorter-lived and often does not reach 10 years of age.
As in humans, on average females live longer than males. Why? Neutering and Spaying . Desexed dogs tend to live longer than intact dogs.
Dogs which are properly feed and kept, on average, live longer than those that are not. In extreme cases, much longer. Important factors are: diet (Phil recommends Eukaneba, and Royal canin foods), regular exercise, obesity control, veterinary attention and veterinary dental therapy as needed.