It's not that simple and sadly: "probably" doesn't always work out the way you want it to. For every Dot Cotton puffing away into her 90s, there is someone who dies in their 20s.

Fairly recently: https://www.bbc.co.uk/news/uk-england-london-56801794 yes, the girl suffered from diagnosed severe asthma. The Coroner gave air pollution as the cause of death. Who knows what would have happened if she was a smoker, but I think we can make an educated guess.

My mum suffered from severe asthma (and hay fever) - enough to have to go to hospital on many occasions. However she never lived in an environment like that girl nor did she really smoke. Oh apart from three years in London and that was back when lead was in petrol. Hmmm.

Anecdotes are not data but I do recommend you avoid fags. Relying on the usual "my gran smoked woodbines until she was 105 and tripped over her old man" is not a particularly clever life choice.

With hindsight I bothered to notice loads of effects that I had glossed over for years.

On average, you are still not going to see the effects of smoking for many years to decades. You might get some exceptions but almost all cases it will take many years of pretty heavy smoking.

I smoked. In the end the best way to stop for me was to take up cycling because I found them fundamentally incompatible. My chest didn’t like it. This was in my 20’s and I was riding 2-6 hours a day.

Endorphins from exercise is a pretty good alternative for smoking.