Hi Al,
Over the years my Heckels lived as long as the other wild discus have.
Most of the problems people will have with Heckel survival is during the first month or so. They are usually very run down of still bearing bite damage that happened in the wild or by predator fish in the net but given a reasonable amount of care they healed well.
The acclimation period is when every effort should be made to provide them with their native water conditions otherwise many will die.
I use water prepared to no more than pH of 6.0, 10-20 ppm TDS and peat filtered. I do elevate the water temp 88dF only reducing it to 82-84dF as they build back their weight and appetites.
Once the have recovered they are a hardy and resilient fish.
As we have discussed Heckels do best when kept with their own kind. They are not as assertive as the other wild discus(all things being equal)and so do not compete well with blues or Greens the same size.
They have never had to.
The longest I kept Heckels which were very large adults when I received them was 5 years. Then they were sold. That means the Heckels were at least 7-8 years old and still in prime condition.
It was in this group of Heckels that I had one pair? that continually guarded and cleaned a flower pot. That was 1968 to 1975. The beginning of my breeding discus.
We sold our fish shop and I continued breeding discus for wholesale sales.
Larry W