My grandmother lived to 100, and only quit smoking because she moved in with my mother, who had a congenital lung disorder. When my brother asked why she waited until age 97 to quit smoking, she said, "Son, those things will kill you!"
Genetics has to be at least part of the answer - "peasant stock" - but my mother apparently didn't inherit those particular genes, having passed on at the tender age of 84.
I may have some of them, because when I had a chest x-ray at 48, the doctor couldn't believe I was a smoker. So I quit while I was ahead. I'd been smoking since I was 14.
My abuela (mom's mom), who lived around all that cigar smoke, outlived him by 17 yrs. She passed on peacefully in her sleep last year at age 95.
I definitely think genes have a lot to do with living a long life (or short), regardless of your lifestyle. Both of my grandfathers chewed tobacco, ate food cooked in lard, and generally ate everything the food nazis tell you not to eat, and they both lived into their mid-90's.