Here are the results of some large studies:
On average, smokers die 14 years younger than nonsmokers.
Approximately 50% of smokers ultimately die from smoking, and 50% die from other causes.
In other words, if you are a smoker, you have a 50% chance of avoiding death due to smoking (although you will likely suffer from health problems. If you are a smoker, you have a 50% chance of dying due to smoking – at an average age of about 28 years younger than you would have otherwise died.
I don’t know how to encourage someone how to get over the addiction, but the statistics are terrifying.