The Ents are ponderous long-lived beings--and the contrast is all too clear.

But I agree that the cyclical nature of human life is very deeply ingrained in the way we think. We are all raised to replace those who came before us, and then are replaced in our turn: basic phenomena like father-son rivalries have their roots in this. What happens if nobody ever gets replaced? If nobody ever retires? It must be impossible to get tenure at Tirion University.

The only thing I can think of is that Elves make their own cycles in a way: that they shift interests, from time to time, and keep trying new (or old but near-forgotten) things.