This I think is a very perceptive point about the brilliance of the album and Davies' vision. He extols the virtues of nostalgia in a changing world and at the same time urges us to accept the inevitable demise of our happier state. Practically every Kinks song is a memento mori. Check out the last song on the last studio Kinks album, "Scattered" for what is (at this point) their ultimate statement about impermanence.