There's really no average age at which smokers die or even most smokers.
Some smokers live only 40 to 50 years and some smokers live 65 to 70 years before they die of smoking and lung cancer or other lung issues.
Then again my Grandpa smoked since he was 18 years old and lived to be 100 years old and smoked everyday of his life and never had any lung issues.
So it can vary as to when a smoker will die.
Most smokers do die sooner than non smokers though and they develop lung cancer and other breathing and lung issues.
Emphysema is another common condition among smokers and you can die of that as well.
I had an aunt who died at age 67 years old and she had Emphysema and other breathing conditions and she died within a few years of being on oxygen.