This isn't really an ideal place for this question, but I understand you must have a lot of stress and worry about your dad. I don't have exact stats, but the first answer is - he has longer having had the bypass than he would have otherwise! If he takes all the meds and follows all the advice to reduce his risk as much as possible (not smoking, good diet, exercise, controlling diabetes if applicable) then he will give himself his best chance of continuing a long life.
Anecdata, but I not infrequently see patients who had CABG 15+ years ago and are still doing well. My own dad had one at 67 too, and has made a good recovery three years on. All the best to yours.