Your father appears to have had a fantastic success and has really dedicated himself to the new lease on life the transplant has afforded him. Although the time to failure of the transplant is proportional to the time since implant, no one can say when his heart will fail. The most common cause at this point is the development of coronary artery
disease,probably due to some autoimmune response. Since the transplanted heart does not cause chest pain
in the typical way it is important to monitor your father on a regular basis, especially looking for occult coronary disease. I have seen patients live longer than 15 years and I wouldn't worry over the comments made by someone who also is dealing with the same issues and is covering up his own insecurities by making jokes. I am certain it can be very difficult to have a transplant as it is a major change in one's lifestyle. I would recommend to enjoy every day with your father, good advice for us all, and if he remains this active and compliant with his doctors he may out live us all. God bless.