To the ancient elves who existed during the time of Arlathan, uthenera was an act of reverence. Elves did not age. They were not immortal, but they did not suffer from deterioration of mind or body. They suffered only from a deterioration of the spirit.
It did not happen often, but the oldest of the elves were said to reach a point where they became weary of life. Memories became too much to bear, and rather than fade into complacency, they voluntarily stood aside to let newer generations guide their people.
Uthenera means "the long sleep," in which the elder would retire to a chamber that was one part bed and one part tomb. To great ceremony from all the extended family, the elder would succumb to a slumber from which they would not wake for centuries, and often never. In time, the body would deteriorate and the elder would die in truth. All the while, family would continue to visit the chamber to pay respect to one who made such a great sacrifice.
With the arrival of humans and the quickening of elven blood that ensued, the practice of uthenera began to fade. When Arlathan fell, it ceased forever.