[Joy]

Arwen, some couple of hundred years?? Let's say a couple of thousand!

Arwen was born in year 241 of the Third Age, the War of the Ring began in 3018 of the Third Age.

As for the Elves aging, he is a quote from the Laws and the Customs of the Eldar from Morgoth's Ring - HoME 10.

Morgoth's Ring (HoME X)
Of the Laws and Customs Among the Eldar
Ælfwine's Preamble

The Eldar grew in bodily form slower than Men, but in mind more swiftly. They learned to speak before they were one year old; and in the same time they learned to walk and to dance, for their wills came soon to the mastery of their bodies. Nonetheless there was less difference between the two Kindreds, Elves and Men, in early youth; and a man who watched elf-children at play might well have believed that they were the children of Men, of some fair and happy people. For in their early days elf-children delighted still in the world about them, and the fire of their spirit had not consumed them, and the burden of memory was still light upon them.

This same watcher might indeed have wondered at the small limbs and stature of these children, judging their age by their skill in words and grace in motion. For at the end of the third year mortal children began to outstrip the Elves, hastening on to a full stature while the Elves lingered in the first spring of childhood. Children of Men might reach their full height while Eldar of the same age were still in body like to mortals of no more than seven years. Not until the fiftieth year did the Eldar attain the stature and shape in which their lives would afterwards endure, and for some a hundred years would pass before they were full-grown.

Morgoth's Ring (HoME X)
Of the Laws and Customs Among the Eldar

[...] It might be thought that, siince the Eldar do not (as Men deem) grow old in body, they may bring forth children at any time in the ages of their lives. But this is not so. For the Eldar do indeed grow older, even if slowly: the limit of their lives is the life of Arda, which though long beyond the reckoning of Men is not endless, and ages also. Moreover their body and spirit are not separated but coherent. As the weight of the years, with all their changes of desire and thought, gathers upon the spirit of the Eldar, so do the impulses and moods of their bodies change. This the Eldar mean when they speak of their spirits consuming them; and they say that ere Arda ends all the Eldalië on earth will have become as spirits invisible to mortal eyes, unless they will to be seen by some among Men to whose minds they may enter directly. [...]

Hope this helps.