There's no way to accurately predict your specific odds of developing a health problem. Statistically speaking, they increase EVERY TIME YOU LIGHT UP. Conversely, when you quit, every time you DON'T SMOKE a cigarette you would have in the past, your risk of getting ill from smoking decreases.
Smokers benefit almost immediately from quitting. Within 20 minutes, blood pressure and pulse begin to improve. After a day, most of the carbon monoxide will be gone and some will already notice improved shortness of breath. After one year, the heart attack risk drops 50% and similarly after 10 years, the lung cancer risk drops 50%. The risk of stroke normalizes after 5-15 years and the risk of heart attack normalizes after 15 years.