My Dad Had Quadruple By Pass About 18 Years Ago,

my dad had quadruple by pass about 18 years ago, then he had another double by pass 2 months ago. he has been hospitalized 3 times with in last 2 months because his lungs got filled with water. now they have finally found that only one of his artery is working and that the rest are blocked. my dad is 70+ years old and the doctors say that his arteries are too weak for any other procedure. what is the life expectancy in a situation like that?