How does the swan's condition in "The Wild Swans at Coole" by William Butler Yeats contrast with that of the speaker's?

The swans contrast with the speaker in this poem.

For the speaker, time passes and nothing lasts forever, and the speaker is all too aware of the passage of time.

For the swans, however, "their hearts have not grown old." They are "unwearied" and, it seems, unchanged. They are mysterious and beautiful, unaware of time.