[Anguirel]

Did Eldacar, King of Gondor-who was half-Northman-live for a significantly shorter period than his predecessors? I don't recall so.

I always imagine Numenorean gifts as being more engrained in the spirit than running in the blood or genes. Denethor and Faramir had them, but not Boromir to the same extent.

I don't see any reason why, for instance, Faramir's son should live for a shorter span than his father because of being Eowyn's son too. I expect that Faramir's inherent spirit of Westernesse would pass itself down.

The Castamirioni were pure as anything, but that didn't help them. The "grace" of Numenor, if you like, had apparently been withdrawn from them.

So I would lean towards the "moral weakening" point of view, despite Formendacil's argument, which applies to the Kingdom of Arnor and Arthedain but not to the remnant of the Dunedain. Gondor had preserved its Kingdom and its wealth, but this was bound to lead to a more hubristic, lax moral state-which the Rangers, struggling for survival, would escape.

(We have to remember that Tolkien is no Hobbesian and in his world hard times always breed altruism better than easy times do. Hence we have the Rangers guarding the Hobbits, and that kind of thing, despite-or because of-their desperate state...)

A more simplistic and perhaps boring explanation might be simply the presence nearby of Rivendell, containing the greatest Healers of Middle-earth. Presumably Elrond's aid should at least be factored in.