[Ibrîniðilpathânezel]

Personally, I have always rationalized Círdan's aged appearance as a combination of true antiquity (awakened at Cuiviénen, or at the very least born there) and stress of a sort. There is a presumption that Círdan wanted to remain in Middle-earth, and while that was in part true -- he chose to stay to search for Elwë, and agreed to Ulmo's behest that he stay because he would be needed -- I don't believe it erases the possibility that he nonetheless longed to sail West, to Aman. Events of the First Age were stressful, all by themselves, and Círdan participated in many of the battles. He fostered Gil-galad, and one could assume that part of why he remained at the end of the FA was because his foster son chose to remain. Comes the Second Age, longer than the First, with a lot of stress in which Círdan is again a participant -- and at the end of it, his foster son is killed in combat with Sauron, who though defeated is not destroyed. Why didn't Círdan sail then? He'd lived through a lot of death and destruction, probably had his heart broken several times -- and yet he stayed. In the Third Age, he hands off Narya to Gandalf (do we know what effect such a sacrifice, even willing, has on a Bearer after they have borne the ring for over a thousand years?). After that, he becomes more reclusive. We know he sent troops to fight against the Witch King, but I don't recall if he went with them. He sends others, like Galdor, in his stead to important councils. Why? It seems to me that something happened to make Círdan more detached from the affairs of ME during the TA. For all we know, he is feeling a powerful version of the sea longing, and may well have been feeling it since long before Galadriel was even born. How many years before that pressure and other stress take their toll on an Elf's physical appearance? We know that psychological stress ages humans before their time; I think it not impossible that it might also do the same to an Elf. Círdan's beard may be an outer manifestation of his inner feeling that he has become bound to the mortal lands of ME; though he longs to sail, he feels he cannot until his purpose there is fulfilled -- and he has no idea when that might at last come to pass.

This is just my rationale. Tolkien never said any specific of this sort, but to me, it makes sense in light of those things we do know for certain about Círdan.