Can an ex-smoker live healthy to an old age?

Yes. Statistically speaking, both non-smokers and ex smokers are likely to live to a healthier old-age than smokers. Of course there are exceptions to every rule. George burns lived to be 100. He smoked 18 cigars a day and drank. At 92 he was asked what his doctors had to say about his lifestyle. "what can they say? They are all dead!".
Hopefully. Although it may not affect every individual this way, it's felt that each cigarette you smoke in your lifetime reduces your life expectancy by seven minutes. Do the math.