Correction: the median post-heart-transplant survival time seems to be a little over 10 years now, so the mean is probably close to that.. However, it's important to note that organ transplants aren't performed just before the patient dies of natural causes, so there's overlap between post-transplant survival and the lifespan the patient would have had without a transplant.

Case in point: An acquaintance with COPD had a lung transplant, then died a year later of related causes. His condition at the time of the lung transplant wasn't good but wasn't that dire; it's quite possible he would have lived longer and had a better QoL without the transplant.

The national registry on solid organ transplants is at http://www.srtr.org/, if anyone wants to do some data mining.