Mabon makes an interesting comment when he states:

"Talking about Gods, Eru obviously amputate Elves from any need for change… So finally when the Three rings lose their powers, Elves decide to leave the Midlle Earth. To me that means Elves were uncapable to cope with the fast –changing environment. As if they were afraid to take the challenge of a New world born. And I thind that Eru’s Divine Plan included this as well."

And further goes on to say the Elves are childish in the way they cannot change.

I work with very young children, and I agree with the fact they have difficulty at times dealing with what to adults seems like obvious and normal change. However, children themselves grow and change very quickly. They work towards integrating themselves into the "grown-up world". Children, by and large, deal with change better than adults because they're designed for it.

I would actually argue the Elves represent the elders...yes, it's not original, but fits more into the general human development model. These are beings in many ways in the height of their wisdom, knowledge, and accomplishment. But yet, there is something that lets the elders know that they must gracefully leave the stage. This is met both with sadness, but yet excitement and even relief by those in the next generation. And, it always seems, the next generation will never quite live up to the Golden Era that Grandma and Grandpa lived through, even though the "good old days" often, in reality, wasn't always that good.