Daniel Deronda was George Eliot's last book, and the level of maturity that she reached in her own life sometimes comes right to the surface of her writing. Sure, the characters we spend the bulk of our time with are angsty twenty-somethings, but the narrator who filters their experiences over to us has a tendency to break out into a "been there, done that" voice from time to time.
One way that the narrator achieves this tone is by constantly reminding us that what happens in the novel actually happened ten years ago – we are reading from the perspective of a reader in the 1870s, while the plot actually unfolds during the 1860s. It's easy to seem old and wise when you can say, "Oh, but that was a long time ago, and we've come so far and learned so much since those days."
Another way the narrator shows off his or her worldliness and experience is through the way that he or she describes the characters of the novel. Sometimes it seems that the narrator finds it easier to relate to the older characters – Mrs. Davilow and Sir Hugo, for example – than to the younger characters with whom we spend a bigger chunk of our time.