What is the life expectancy for someone with emphysema?

Depends; many things: ...Can affect life expectancy with emphysema. How severe is it, how limited is your exercise tolerance, have you ever been hospitalized to treat an exacerbation? How limited are your activities and what other ailments do you have? (coronary disease, heart failure, cancer, etc., ) there is no text book with the answer to this question, and even knowing all this won't lead to a very accurate answer.

Depends: It depends on the severity and other medical conditions which coexist. Many emphysema patients die of other causes. Frequent flare ups leading to repeat hospitalizations, or repeated respiratory infections are poor prognostic indicators.