Just had a conversation- actually twice- that I think is worth putting on tumblr, and it's this: the role of princes and princesses in elven society.
Because when a king or queen is expected to live hundreds or thousands of years- perhaps indefinitely (until world's end)- what is the point of a prince or princess?
And I think it's because we are looking at it through such a human lens, with the first meaning of the title being heir. The one who will rule next.
I firmly believe that an elven prince or princess is- first and foremost- a role. They are ruling in their own right over a set domain, under the king or queen, and in partnership with them. And to me, it makes the most sense that the king or queen rule the country, while the prince or princess rule the household.
And that is not a minor role! Think about it- there is so much that goes into the governing of a house (or castle, or flet, or whatever). The welcoming and care of guests/diplomats is political, as is hosting and managing feasts. Resolving disputes, from ministers to servants, is imperative (and excellent training). And who is overseeing the finances, the food stores, the repairs, the local contracts? Is Legolas helping to manage the imports/exports of wine and butter with nearby towns? Does Luthien help in the care and conservation of the nearby forest, and notate the harvest and stores? Is Idril responsible for the care of young Hurin and Huor in Gondolin, making them feel welcome and at home? And does Arwen- though not a princess- lead those who take care of the textiles; not just the creation of them, but the repair, restoration, and cleaning of everything from fine tapestries to bed linen?
And they are, by default, representative of the king or queen. Legolas was sent on a diplomatic mission to Rivendell. Finrod needed to appoint Orodreth specifically, because there was no prince or princess of Nargothrond.
And the whole conversation was centered around Luthien. Because it certainly adds an extra layer to her running away from Doriath. For the love of a mortal, Luthien abandoned her role and her duty, and betrayed her people. This can't be overlooked!
(It's a very strong parallel with Eowyn, actually. The wrong isn't that she went to war, it's that she abandoned her post.)
In conclusion- honestly "prince" and "princess" is so nebulous and multifaceted, it's worth exploring. It adds depth to both the title and the characters.