Writing a successful TV series must be a thrill. Beyond the money and the Hollywood job security, you can continue doing what you love season after season, exploring the back alleys of your narrative, devoting entire episodes to side characters and plot detours. You get to carry your story forward, and forward some more, exploring and expanding on your original premise. You get to devise long-term plot arcs that will inspire the viewer to stay in the car for the whole ride.

As Stephen King once said, “In series TV, it’s beginning, then middle, middle, middle.’’ You start your show, and then you write the middle, and more middle, and even more middle — sometimes, in the case of long-lived but creatively deteriorating series such as “True Blood,’’ “The X-Files,’’ and “Glee,’’ far too much middle. For years, your goal is to keep providing middle, and to avoid dead ends at all costs. And then the ax comes down, your show is ending, and you need to do what TV writers do least of all — write a series finale. Despite being wired to stretch things out, you suddenly need to wrap it up.

So pity the TV writers who face a task that is the antithesis of what they generally do. Forgive the ones who botch it big-time, epic finale fails that include “Lost,’’ which ditched years of accumulated clues in order to give us a woo-woo gathering in some kind of limbo, and “Dexter,’’ which had our vigilante murderer fake his own death and live on as a depressed lumberjack with a bad beard — just in case the possibility of a revival rears its head one day. Most famously, “Seinfeld’’ didn’t conclude so much as crash and burn, with an overlong episode overstuffed with cameos and flashbacks — almost like an infomercial for the show’s syndication run.

And, most important, celebrate the TV writers who buck the trend and pull off their finales beautifully, who make endings that stay true to the tone of the series, give the lovingly attached viewership a sense of emotional catharsis, and somehow conclude the storylines by tying up loose strings or creating some deliberate ambiguity. The brilliant finale of “Six Feet Under’’ flashed forward to the deaths of all the characters, tying up the strings forever on a show about death. “The Sopranos,’’ on the other hand, delivered pure irresolution — a cut to black — and let us decide, individually, whether we wanted Tony to die or not. Both worked, albeit in very different ways.

I’m thinking about finales, and feeling appreciation for those that work, because this past week we got a good one from the makers of “The Americans.’’ Really I should say “another good one,’’ because, despite “Dexter,’’ we’ve had some luck with series finales in recent years, including those for “Breaking Bad,’’ “Justified,’’ “Friday Night Lights,’’ “The Shield,’’ and “Mad Men,’’ with its wise, comic, and utterly perfect cut from Don meditating at a spiritual retreat to the “I’d like to buy the world a Coke’’ commercial. Perhaps the loud anger toward “Lost’’ after its 2010 finale has served as some kind of cautionary tale?

For me, “The Americans’’ went out very nicely after six seasons, with a somber, quietly tragic episode. It wasn’t “Six Feet Under’’ good; that kind of concluding glory is rare. But it satisfied me, both as a critic and as a viewer with some emotional attachment to the characters. Instead of killing off Philip, Elizabeth, Paige, and/or Henry Jennings as some kind of punishment for all the dastardly espionage, the writers took a more circumspect approach. At a critical point in the last episode, Russian spy Philip says to gun-wielding FBI agent Stan, “We had a job to do’’ — the only justification Stan could understand. And he did understand. He has a similar job to do. After all, the show implied, enemies in a war — in this case, the Cold War — are all human beings.

And Philip and Elizabeth were punished; they most likely will not see their children again. Nonetheless, despite having lived a fake marriage for decades, they were now a genuine team, facing their changed native country together. It was grim, but with a tinge of optimism as the end of the Cold War approached, and it was true to the spirit of the entire series.

Series finales are just an hour or two, while the rest of the show lasted for many hours — for “Breaking Bad,’’ 62 hours, for “Dexter’’ 96 hours. So why does the finale matter so much? In the case of a puzzle show such as “Lost,’’ it provides the solution we’ve been working toward all along. It justifies all the work we put in. But finales also determine a show’s legacy to some extent — for example, if Tony Soprano had died, “The Sopranos’’ might now seem more like a morality play, with its central killer paying for his crimes. Some enjoyed the “St. Elsewhere’’ finale, which made the entire series into the daydreams of an autistic child, but it reduced all the previous episodes to something less realistic than we’d thought. Indeed, it erased the meaning of almost everything that came before it.

So I’m delighted to see the art of the finale improving. Like scripted TV in general, finales are beginning to deserve our attention and not just our disappointment.

Matthew Gilbert can be reached at gilbert@globe.com. Follow him on Twitter @MatthewGilbert.