The repetition in "Break, Break, Break" both suggests the consistency of the speaker's grief and also its slow-but-steady evolution. The second line of the final stanza sounds like the second line of the first stanza, but with a slight difference. The speaker seems to argue that time keeps progressing without change, in spite of his great loss, and yet there are lots of little changes, like in the phrasing of those lines.
The similarity between the first two lines of the first stanza and the first two lines of the final stanza suggests that time passes unchanging; however, the slight difference in word choice between lines 2 and 14 shows that change can occur over time, however slowly.
Time seems to move more slowly for the speaker of "Break, Break, Break" than for the people around him; his grief has placed him outside of normal time.