Faramir's age.

[Belegorn]

Originally Posted by Bêthberry

If death is supposed to be a gift to the race of man, then why is longevity such an important issue? Why are the "high" supposed to live longer and why is a decrease in life span a sign of weakness or decline?

To your last enquiry in Appendix A it is said, "their years lessened as their fear of death grew" [p. 354] The decline in their lifespans was in conjunction with their continued rejection of the fate of Men. This is basically the shadow that fell upon Numenor as the Edain, "began to long for the immortality of the Eldar... in the days of Tar-Minastir, eleventh King... the thought of death darkened the hearts of the people." [RotK, p. 353]

The people were not accepting their fates. They grew resentful of the choice of Elros to be a King of Men rather than of the Elves. They thougt they should be given a choice too to decide their fates and many of them wanted to be immortal as the Elves were. Keep in mind how far this dread of death went; they began sacrificing people to Melkor in the hope that they could be released from death when Sauron had the ear of Ar-Pharazon. This afflicted even the Faithful so that even their lifespans diminished yet not nearly as fast as the Kings. In the Akallbeth the general feeling on the island is described as, "the desire of everlasting life, to escape from death and the ending of delight, grew strong upon them;" [Sil., p. 325]

As regards the fate of men an envoy came to admonish the people of Numenor, "this we hold to be true, that your home is not here [in Arda, that is, which is why the Elves referred to Men as visitors], neither in the land of Aman nor anywhere within the Circles of the World. And the Doom of Men, that they should depart, was at first a gift of Iluvatar" [p. 327] The King Atanamir was not hearing this and did not agree with this and he "lived to a great age, clinging to his life beyond the end of all joy; and he was the first of the Numenoreans to do this" [p. 328]

Longevity of a life 3 times that of the span of average Men for the general Dunedain was a gift. This was a gift that did not contradict their natures, but they wanted more, they wanted to be as Elves, even though they nearly were, "they grew wise and glorious, and in all things more like to the Firstborn than any other of the kindreds of Men" [Sil, p. 321] The distinction between the two, the High Men and Elves was barely perceptible. So why are the High Men supposed to live longer? It was one of the gifts given to them like the island of Numenor, "As a reward for their sufferings in the cause against Morgoth" [RotK, p. 351] in the First Age. They were Elf-friends. Longevity should not have been an issue for them since they were mortal and could not hope for immortality, though some assume maybe Tuor was granted immortality as Luthien was granted mortality.

[Zigûr]

Originally Posted by Belegorn

It was one of the gifts given to them like the island of Numenor, "As a reward for their sufferings in the cause against Morgoth" [RotK, p. 351] in the First Age.

I think this is a rather pertinent example. It would seem to me that the long lives of the Dúnedain were both a reward and a responsibility - so that these Men would have a long time to attain wisdom and therefore see to their inheritance, the governance of Arda, with justice and righteousness, but also so that they had the time to appreciate the fruits of their labours. Yet not endlessly, so that they avoided the weariness of the "terrestrial longevity" which was the burden of the Elves and the incarnate Ainur. For instance when Gandalf is talking to himself and says it is "a habit of the old", Aragorn responds: "I am no longer young even in the reckoning of Men of the Ancient Houses. Will you not open your mind more clearly to me?" (LR p.485) This longevity was seemingly an assistance to their spiritual mission, as it were, for it lent them the experience and time needed to fulfil the responsibilities of their age. On the other side, it's said when Aragorn and Arwen are married that "the tale of their long waiting and labours was come to fulfilment." (LR p.951) A long life was not an unenviable thing; it was a reward for labours. But an endless life was not such a blessing: "Thus you escape, and leave the world, and are not bound to it, in hope or in weariness." (The Silmarillion .265)
I would offer, therefore, that a long life was meant as an opportunity and a responsibility to fulfil one stage of Eru's plan for Men in the greatest possible way, before passing beyond Eä to experience the next stage of the spiritual journey ordained for Men by Eru: that which occurred after the death of the body. I would consider that to be a possibility for why a long life would still be considered valuable even if mortality was regarded as a gift. It effectively allowed a Dúnadan to have the best of both worlds.

[Belegorn]

Originally Posted by Zigûr

the long lives of the Dúnedain were both a reward and a responsibility - so that these Men would have a long time to attain wisdom and therefore see to their inheritance, the governance of Arda, with justice and righteousness, but also so that they had the time to appreciate the fruits of their labours. Yet not endlessly, so that they avoided the weariness of the "terrestrial longevity" which was the burden of the Elves and the incarnate Ainur.

I read somewhere, maybe a note, maybe not, how they were granted long life enough not to sort of break their natures, because their bodies could not handle such things in excess of that they were given and also their Doom. I agree with you that they should have no share in the burden of the Doom of the Elves when they had their own Doom to embrace.