It’s been an unexpectedly emotional week in front of the TV, alternating between a backlog of recent episodes of “Late Night with David Letterman” and the entire run of “Mad Men” (AMC, 10 p.m.).

Letterman’s retirement is something we’ve seen coming, but the last couple weeks of shows have been extraordinary, relaxed, with the very best guests and superbly curated combination of songs and musical performers. There’s a lightness in his mood and a diplomacy with which he’s received his deserved accolades.

“Mad Men,” too, had an expiration date as the 60s ran out. But immersing myself in the current marathon of all seven seasons of the show, leading up to the finale tonight has made me much more appreciative of all it has accomplished and the consistently high quality with which every episode was made.

More than once I’ve stood and said of both shows, This can’t end! Something must be done! Somebody do something! It’s almost a matter of preserving a segment of American culture and experience and holding on to it.

Watching “Mad Men” in particular, I’ve been struck at how many scenes have stayed with me (Sally walking in with a dry cleaning bag on her head was the first time we saw her in episode two). In other episodes, it’s been enriching to see other characters slowly develop (Megan, lurking in this job or the other in the office before Don takes her to Hawaii) or early appearances of people who would make bigger impact later (that dude from McCann).

There are characters, too, who have since become familiar in other roles. Zosia Mamet (Shoshana on “Girls”) was the lesbian photo editor of Life who worked in the building and hung out a bit with Peggy; Danny Strong (creator of “Empire”) was the nephew of Roger’s fiancé who they had to hire. There are dozens more. What actor wouldn’t want to be part of this show? Which among them have not capitalized on any connection to it?

I’m not one to go back and which entire seasons of something I’ve seen (there’s too much pending to watch to allow for the time). So it’s a revelation to see stories develop, knowing, as Megyn Kelly would say, what we know now.

Pete stayed married much longer than I thought; Megan and Don only broke up last month, when the second half of the seventh and final season started. The “Fat Betty” period only lasted a few episodes.

I’ve done my share of single episode recaps over the years, where a common complaint was that there wasn’t enough time on the ad business in the office. Now, I see that practically all the action took place in the office. They were banging out proposals and setting campaigns on a weekly basis. The personal stuff seemed to be peripheral.

All this Don has given me a new feel for him: one of pity. Here’s a guy who never really knew who he was and couldn’t talk to anybody about it either. He was gruff and unfeeling and a bit of a jerk, but he loved his kids and, though his expression, showed that he felt sorry for how he treated them. He brooded a lot and put away more booze than some small European cities. He napped regularly.

I’ve got a strong personal feeling toward “Mad Men” as well since the time AMC first introduced it to critics with a party at the old Beverly Hills Friars Club. There, with waitresses (and the cast) in period garb, Jeff Goldblum’s jazz trio played on a stage and I ended up in the upstairs pool room, its floor covered in an inch of sand to serve I guess as an immersive ashtray, and where, amid the dust and smoke, I played a round of pool with its stars.

As a writer for the Hartford newspaper, I had sort of an in as one actor, Michael Gladis, was from nearby Farmington. He very graciously gave me an interview there and met me when I returned the next year to visit the set of what was already a successful show.

Jon Hamm, as it happened, is entwined romantically with Jennifer Westfeldt, the actress, writer and director, who I had interviewed before because she was also from a Connecticut town, Guilford. So I got to talk with them quite a bit.

Critics loved “Mad Men” for its tone, attention to detail and cinematic sweep and creator Matthew Weiner appreciated critics for spreading the word. So he’d come to the TV Critics Association awards and hang out afterwards, and make a point to assemble a party in addition to the occasional press conferences about the series.

Most recently, I got to see Weiner, Hamm, Christina Hendricks and John Slattery when they came to donate props and wardrobe to the Smithsonian. By now I was in Washington and freelancing for Smithsonian Magazine and writing about it.

But there was a more primal connection to “Mad Men” as well. My father was a salesman, my mother the kind who entered contests and thus paid a lot of attention to ad companies that sponsored them. I grew up in the 60s and the look and feel of the series certainly spoke to me (though I’ve always had a problem with how they undersold youth culture and the Beatles invasion in particular).

Eventually, the characters became people I cared about, just as they have for millions of other viewers, in a long, extended movie that comes to an end with some considerable sadness tonight. Just seeing how Sally has grown up before our eyes in the seven seasons is enough to make eyes well up.

To suggest how it will all end does a disservice to all the surprises that have happened heretofore on the series It won’t wrap neatly. It will suggest that life goes on beyond the series. That Betty has been diagnosed with cancer is a bitter consequence of a show that singularly brought chain smoking back to TV, quite realistically. A reunion between Betty and Don, even at her deathbed, is probably the best resolution anyone can expect. We’ll see what happens.