Hello. Thank you for your question and welcome to HCM. I carefully read your query and understood your concern.
In this scenario, we can only speak statistically, otherwise we would be speculating. There are no clear-cut references that can be attributed to a person, and to be arbitrary and say a number of years remained.
However, we can focus on statistics about bypass grafts. There is a bypass blockage probability of 8-10% in the first year, and up to 50% in ten years, when saphenous vein grafts (SVGs) are used. This probability is much lower when left or right internal mammary
artery (LIMA or RIMA) are used, because arteries have features that veins do not have. It is normal for him to feel great because coronary artery bypass grafting (CABG) is one strategy of curing coronary artery disease. I would recommend a diet rich in fibres (green or dark green leafy vegetables), low on red or raw meat, if none, but more with fish and chicken and other poultry, low on salt and slight physical activity, for an hour a day. Alcohol and tobacco should be withheld.
I hope I was helpful. Take care.
Kind regards,
Dr. Meriton