Those are some powerful claims, do you have any links for that? Generally 2-pack smokers that started early ie in their 20s or even earlier don't live till retirement where I live, but I agree its a small sample and generally such people don't live a healthy life overall.
and the more ways you add risk through your live the more likely you will die an early death
it's just basic statistics
and for the same reason you will find someone who does add all the risks but somehow still dies with 90+, if your sample size is large enough and factors complicated enough you are pretty much guaranteed to find some pretty big outliers
but realistically speaking it a pretty bad idea to assume you are such an outlier, but many people tend to ("basically") do exactly that (due to an combination of subconsciously avoiding reality and simply not thinking things through)
A couple of sources putting the life expectancy cost at 10-20 minutes per cigarette.
Smoking for 40 years that would be 5 months at 1 a day or 17 years at 40 a day.
I think that's all consistent with what you said: 2 packs a day and you usually, but by no means always, don't make it to retirement at ~66. Five months is enough that I'd take some care to avoid it, though.
