Change and moving forward is one of the themes of Mad Men. The characters are going through transitions quickly. Compare any character in Season 1 to the same Character in Season 7 and the change will be astounding. Even Bert Cooper who never changed much at all - now he's dead!
As I have been working through this wiki I see the need to update it. The task is gargantuan, but I say . . . prepare to take a great leap forward! Prepare to swim the English Channel and then drown in champagne!