Genetic studies have shown that a majority (55%) of how long you and I will live is determined at birth, by genetics, by how long our ancestors lived. How we choose to live, the care or lack of it we take of ourselves, diet, exercise, substances we abuse, mental composure, etc. only account of 45% of lifespan variation.
If your family live to be old, chances are you will also. If not, the chances of attaining old age are substantially less good.
This doesn’t mean you can’t improve your chances by refraining from substance abuse and living in a healthy fashion, you can. However, the improvement you achieve will probably be measured in years, not decades.
A surprising number of the elderly did (and in some cases still do) unhealthy behaviors, but they have genes that can handle the abuse and carry on.
