Life expectancy is something that varies, not only between breeds of dog but also between individuals within a breed. A dog's life expectancy is not only determined by breed, but by care, individual genetic disposition and nutrition. With that in mind, average life expectancy ranges can be calculated based on characteristics of breed genetic dispositions.
Purebred Lab Statistics
A black Labrador retriever has an average lifespan of about 10 to 12 years. Most purebred Labrador retriever owners can expect their pets to pass away somewhere in that range. Of course, some dogs will live longer while others may die prematurely.
You might expect a dog that is a product of crossbreeding between a Labrador retriever and another breed to have a similar life expectancy, but this may not necessarily be the case. Most mixed breed dogs enjoy a certain level of genetic hardiness that is lacking in purebred dogs due to inbreeding. This trait allows mixed breed dogs to have a longer life expectancy than purebred ones.
Traits of Other Breeds
Labrador retriever mixes may have a different body composition as compared to a purebred dog. For example, a mix may be smaller than its purebred counterpart, giving it a longer life expectancy. As a rule, smaller dogs tend to enjoy longer lives than their larger cousins do. A Chihuahua has an average life expectancy of 15 to 18 years, while Great Danes average 8 to 10 years.
Black labs have a tendency to develop certain diseases that require medication to manage. These medications may contribute to a shortened lifespan. Because a mixed breed dog's DNA is a combination of breeds, it is less susceptible to acquiring these breed-specific diseases and will not require medication, which may also factor into its longer life expectancy.
In most cases, a black lab mix, depending upon size and physical condition, will outlive its purebred counterpart by 2 to 5 years.