As I can see everything seems to be going on wonderfully well with you. Your cholesterol profile is quite good and your exercise level too seems to be good. With this kind of a profile, generally the long term results of bypass surgery are very good. However, to quantify in an individual patient, is impossible. In generic terms, the patency rate of the artery from inside the chest, called left internal mammary artery, which was used for bypassing your LAD, is upwards of 90% at twenty years and that of veins is roughly 50% at ten years. I think what you are doing is correct, so please stop worrying about how long will the grafts last, because if you think much, you would add a risk factor of stress, so be carefree and enjoy your self.