‘And the days of Isaac were one hundred and eighty years, and Isaac yielded up his breath and died, and was gathered to his people old and full of days. And Esau and Jacob his sons buried him.
Isaac lives on for many years with Esau and Jacob as his support. He was not much more than one hundred when Jacob left for Paddan-aram and he had thus many years of life ahead of him. But he was blind and old before his days and there were no special covenants to record. However, as with all the ages of the patriarchs, the number is a round number and therefore probably contains a meaning of its own. The aim is to show a long and successful life. How close he came to those exact years neither he nor we would know. It is extremely doubtful that records of age were kept over so many years.
Meanwhile, after the return of Jacob their wealth of possessions and cattle and herds was so great that Esau eventually removes permanently, with all he possesses, to his well established base in Mount Seir (Genesis 36:6). His visits to his family home will now be far fewer and less protracted. Previously he has shared his time between assisting his father in times of necessity, lambing, sheepshearing, harvest and so on, and leading his band of warriors. Now that can be left to Jacob. But he remained in touch with his family and when his father died he came to join Jacob, and they buried him together.
These words may well have been added as a postscript to the previous covenant record.