I think it depends on many factors. I have border collie/saluki cross who is now 14 and still going strong; no illness or ailments and is extremely active - walking miles every day and though she has slowed a little in the last two years, she still outpaces other younger dogs of different breeds. On the last visit to the vet for a general check-up I was told she had the heart rate (slow) of a much younger dog and similarly with her teeth. Individually as breeds, their average life expectancy is around the same 12 -14 years but this doesn't mean it will always be the case.