My Father Who Is 65 Will Be 66 In Oct.

My father who is 65 will be 66 in Oct. Has had only one actual heart attack at age 37 resulting in a triple bypass. 15 years later he had a double bypass with no heart attack....now we are 15.5 years after the second bypass and issues have developed with color change, and increased in agina and SOB....had a heart catherization done yesterday and two arteries are completely blocked,but has an old graft that is 100% open and functional.....so basically he is functioning with one good artery....what is the life expectancy of some one in this situation that is compliant with diet,meds,and exercise and also of someone that is not. Thanks.