Life expectancy. Heart bypass surgery!

Sir my father underwent a bypass surgery 8 years later when he was at the age of 48 he has mini heart attack at that time when he was completely diagnosed he have diabetes, hypertension,hba1c-10 at that time,he was diagnosed with triple vessel disease of heart with diffuse coronory artery with 99% blockage in heart he was manage with beating heart surgery surgeon who performs surgery on him take svg graft from leg to all three grafts in right coronary artery and take left internal mammary artery lima to lad now after 8 years he was stable and they have very little control on her diet but one doubt was always worry me about his life expectancy because I search it on Google somewhere they show life expectancy was 10 years and somewhere they show 20 year or somewhere more but I want to know the reality about what is the life expectancy of this surgery with this case because every one love his parents that's why I want to know reality about life expectancy of my father heart bypass surgery