Certainly, on a superficial level, we can say that all of the major Mad Men characters journeyed forth through significant life changes. But as much as these characters gained scars and wisdom through their journeys, none of them actually changed over the course of a decade.
The trick of "Mad Men" is that we all watch it and see what's being done so utterly wrong by the characters. We judge them for the choices they make with the wisdom of 45 years of history and change that they could never have predicted.
The song of this episode, interwoven with skill and foreshadowing, is Peggy Lee's haunting, "Is That All There Is?" The underlying theme echoed is the necessity of endings -- of 'letting go,' of severance, in all lives lived well.