What Is His Age?
The first of these two quotes again has the generalizing "we" problem; is Legolas simply speaking as a member of a long-lived race which is used to seeing time in this fashion, or is he speaking from personal experience? The second quote implies that he felt young before he started travelling with the Fellowship. Do elves of any age feel young, or is that a clue?
Fans of the Peter Jackson films have an answer to the age question, but it's actually not from Tolkien:
FergoBaggins of CoE has pointed out that this figure matches the year in which Aragorn was born. But in the writings of Tolkien himself, we've found no explicit references to Legolas' age or personal history prior to the War of the Ring.
To answer this question more fully, we must turn to Legolas' recollections and his family history. This approach is problematic, since we can't tell when he's speaking about incidents that happened far away while he was alive, or when he's speaking about events he only knows through the songs and legends of his people.
(Note: S.A. = Second Age, which began when the ancient Elf-kingdoms were covered over by the sea, and ended with the Last Alliance of Men and Elves about 3000 years later. T.A. = Third Age, which began when Isildur cut the Ring from Sauron's finger. Frodo's quest begins in T.A. 3018.)
When the Fellowship is crossing the Misty Mountains, Gandalf and Legolas discuss the Elves who used to live outside the Gates of Moria, a long time ago:
Legolas' family passed over the Misty Mountains to join the Silvan elves "before the building of Barad-dûr" (Tale of Years, Appendix B, ROTK) which was begun in S.A. 1000 and finished in S.A. 1600. Eregion (Hollin) was founded S.A. 750, so depending on whether "the building of Barad-dûr" refers to the start of construction or its completion, it is possible that Oropher left before Hollin was founded. If so, anyone who had gone with him would know little of Eregion, and Legolas' ignorance of Eregion might be explained away.
However, if Legolas were dwelling with his grandfather prior to his removal across the Misty Mountains, he would have known some of the High Elves that settled Hollin, so they would not be "strange" to him. That suggests he was born after his family had moved east. He certainly never mentions that migration, and his consistant attiude that he is a Wood-elf definitely seems to postdate it. So I think we can be pretty sure he was born after his noble family settled among the Wood-elves and "went native", which was sometime in the early part of the Second Age.
Our next milestone is Oropher's move from the vicinity of Lórien to the northern half of Mirkwood. What does Legolas know about this migration?
It sounds as if Legolas was not alive when his folk still "journeyed hither back to the land whence we came", but it's hard to tell. The fact that Legolas never shows any suspicion or hostility towards Galadriel and Celeborn suggests he was born after the doubts and resentments that led his family to move north in the middle of the Second Age had died down. That pushes Legolas' birthdate up to the latter part of the Second Age at the earliest. Now we get to a sticky problem.
Here we have a quote with a firm date: the Balrog arose in Moria in T.A. 1980, and Amroth and Nimrodel were both lost during the resulting chaos in 1981. However, Legolas seems to have made a mistake. He's forgotten the Elvenking's mighty hall of stone. When was it actually built, and why? When the shadow of Dol Guldur fell upon Mirkwood around T.A. 1000, the Silvan Elves...
Legolas' home is the main "strong place of stone...delved in the ground like Dwarves" among all the Silvan folk; we don't see any such place in Lórien. So he has to have his father's hall in mind. But the event that he says inspired its construction is a thousand years too late. If you assume that the mistake is not Tolkien's, then the most logical explanation is that Legolas was born well after the deaths of Amroth and Nimrodel, long enough for them to be a poignant legend, for the Balrog to be blamed even for things that had nothing to do with him, and for any family grumbling regarding Celeborn and Galadriel (who took charge of Lórien after this event) to have died down. We know the issue was still sensitive at the time. They took the title of Lord and Lady, not King and Queen, "for they said they were only guardians of this small but fair realm" (UT, same chapter), even though Galadriel still had "Queen" on the mind right up until she faced off with Frodo. Legolas seems blissfully ignorant of the politics of the period.
Legolas has also never been to the Golden Wood before. If he were older than two thousand, he'd predate Dol Guldur, and would have been living closer to Lórien. You'd think he'd have visited his closest kin and neighbors at least once, to deliver messages or pay his respects to King Amroth, an old family friend! After all, Legolas left Mirkwood with (he thought) a distressing but minor matter: the escape of a prisoner whose importance was not understood. I simply cannot believe he would never have visited Lórien before it became dangerous to go that way. So I'm putting his birth after Dol Guldur, and feel pretty confident that it's necessary to do so. That pushes his birthdate past T.A. 1000, making him less than two thousand years old: younger than any other elf named in the story. And again, there was enough contact between Lórien and Mirkwood for the Woodland Realm to hear details about Amroth and Nimrodel a thousand years later, so someone was still travelling between them even then. But it wasn't Legolas.
That's another hint, but only a hint, that Legolas postdates their deaths. Are there any more clues that can help us?
Well, we have Tolkien's habit of making parallel generations in closely-allied families: Tuor and Huor, Túrin and Húrin. The pattern here is less obvious, but King Amdir of Lórien and King Oropher of Mirkwood are both Sindar princes of Silvan Elves who moved east at the same time, died in the same war, and were succeeded by sons of the same age. If Amroth and Nimrodel hadn't died during the mess following the Dwarves' discovery of a Balrog in Moria, their children would have been born less than a thousand years before ROTK, and Legolas would be the same generation as their kids. So there's a fourth clue pointing in the same direction.
I also can't help but wonder about Bilbo's mithril coat, made for a half-grown elven prince. The dwarves who settled the Lonely Mountain were fleeing Moria after the Balrog disaster. There was only one Elf-king left in Middle-Earth by that time. For whom was the coat made? Unless Legolas has siblings we never hear about (which is of course possible), that was supposed to be his! So there's a fifth clue, but a tenuous one, since I don't think Tolkien had come up with Legolas when he was writing The Hobbit.
But if we assume that Tolkien did not make a mistake, and that all these clues are not coincidence, then it seems Legolas was born after the tale had been glamorized into legend. That makes him less than eight or nine hundred years old, though old enough to have seen five hundred autumns. Say seven hundred. He would certainly be old compared to the rest of the Fellowship, but as an Elf he's still in his "tweens", as the Hobbits would say, or in human terms, he's a young man just coming into the prime of his life.
After sifting through all of this, I discovered that Michael Martinez, the author of Visualizing Middle Earth, had concluded that Legolas was not much past five hundred years old.
More