Graft survival, even with allotransplantation (human donor to a human host), is not equal to an average human lifespan. It's much shorter (11-16 years on average). Porcine grafts (which often last over 15 years) do not seem to be limited by the average pig lifespan (which, google tells me is 6-10 years). In both allo and xenotransplantation, graft failure and host survival are issues of the immune response to the graft, not of the expected lifespan of the donor.
Will the heart hold-up throughout the lifetime of the human, or will the human need a new heart in say a decade or two?
Lets answer this, first, for a heart transplanted from a human donor, an allograft. Even from a human donor, the heart is unlikely to hold up for a normal human lifetime. Heart transplant survival has improved greatly over the last five decades, but median survival in an adult is now 11 years. In pediatric patients, it's 16 years. The main problems are cardiac graft vasculopathy, malignancy, infection, and immune rejection. Transplant is a treatment, not a cure, and a major challenge of transplant as therapy is managing the immune response. Rejection and graft vasculopathy are (generally) related to immune injury of the transplanted organ. Malignancy and infection are related to immune suppression of the host.
Xenotransplant (transplantation from a non-human donor) adds an additional complication to the challenge of managing the immune response. Here, the range of non-self antigens is even greater, and the graft will be attacked by complement and other aspects of the innate immune system, as well as the adaptive immune system. This leads to graft destruction, often in the first hour after transplant. There have been advancements using transgenic pigs that solve some of these problems, with improvement in survival in pig to primate trials. Personally, I'm skeptical that CRISPR techniques will easily solve all of the problems of transplant immunology, but transgenic animals have moved things forward substantially over the last 15 or so years (see this review)
As far as porcine valves are concerned, they are treated to reduce their antigenicity (a protocol that hasn't worked for cardiac xenotransplants). Paradoxically, graft survival in older patients is quite good, with most valves lasting beyond 15 years. This may have something to do with age related decrease in immune function, but regardless, porcine tissue (at least from a valve), seems to hold up quite well.
There is good access to data on cardiac allotransplant survival (both adult and pediatric) directly from the international society for heart and lung transplant. There is a good review of pediatric transplants here. You can read more about cardiac graft vasculopathy here
As far as xenotransplantation is concerned, there was an excellent issue of the international journal of surgery, november 2015, that has a number of articles reviewing xenotransplant. Many are available without a paywall, and it's a good place to read up on this. This article from that issue discusses immunological challenges in xenotransplantation from pig to primate. You can read more about this here, but it's beyond a paywall. A good discussion of the overall history of xenotransplantation was reprinted in that issue, here