Seinfeld retired to a dressing room, plopping down beside a bucket of bottled water. I congratulated him on the performance. “I’d say two-thirds of that set was garbage,” he said, matter-of-factly. “Whether it was lines coming out wrong or the rhythm being off.” He said he’d counted “probably eight” jokes that failed to get the kinds of laughs he desired. “There’s different kinds of laughs,” he explained. “It’s like a baseball lineup: this guy’s your power hitter, this guy gets on base, this guy works out walks. If everybody does their job, we’re gonna win.” I told him about the khaki guy’s spit take, and Seinfeld cracked up, calling this “a rare butterfly.” Nevertheless, “there wasn’t one moment where I was where I wanted to be. That was just a workout. I had to get it going again.”

Over nine seasons, “Seinfeld” enjoyed an omnipresent, epochal success: you can draw a line from “Seinfeld” to Larry David’s “Curb Your Enthusiasm” to Ricky Gervais’s “Office,” “Arrested Development,” “It’s Always Sunny in Philadelphia,” the American “Office” and out from there to maybe half the sitcoms currently on the air. In stand-up circles, Seinfeld is a towering figure, revered for the sharpness of his eye as he scrutinizes subjects large (marriage, death) and small (answering-machine protocol, 5-Hour Energy drink). In 2001, George Carlin spoke admiringly of “the little world, the kind of world Jerry Seinfeld investigated to a great, high level.” When “Seinfeld” went off the air and Seinfeld began rededicating himself to stand-up, he told Time that he didn’t consider himself great. When I asked him how he evaluates his talent today, Seinfeld demurred before allowing, “I think it’s there now.” He says he plans to do stand-up “into my 80s, and beyond.”

One afternoon not long after the Gotham gig, Seinfeld invited me to his Upper West Side work space, where he spends most days, writing jokes. Clean, modern and cozy, it resembled some hip therapist’s office: a high-ceilinged, poured-concrete box with a long plushy couch, a little balcony and a kitchenette. Framed pictures covered a wall: a production still from the George Reeves “Superman” serial; an original cartoon of Seinfeld and Alfred E. Neuman that ran on the cover of Mad Magazine in 1997; a photo of Steve McQueen with a Porsche 917 that the actor owned in the ’70s and that today belongs to Seinfeld. A sleek Pinarello racing bicycle, which Seinfeld rides around town, stood against a wall. “It’s very addictive, that feeling of gliding through the city,” he said. Some Emmys huddled in a corner beside a ventriloquist’s dummy, which Seinfeld cherishes more than the awards: “I did a comedy show with that in third grade.”

Seinfeld sat in an armchair in a sweater and jeans, resting gray Shox on a footstool. On a typical weekday, after getting the kids (his daughter Sascha, 12, son Julian, 9, son Shepherd, 7) to school and exercising in his building’s gym, Seinfeld walks here, grabs a legal pad and a Bic pen and sits at his desk. No street noise penetrates. The pages of the pad are destined for either a wastebasket or a master file containing Seinfeld’s entire act, handwritten. The other day, perusing this file, he found a joke in which, discussing touch-screen phones, he likens the act of scrolling through a contact list and deleting names to the effete, disdainful gesture of a “gay French king” deciding whom to behead. Seinfeld wrote the joke a year ago and forgot it; having rediscovered it, he’d be telling it onstage that weekend.

Seinfeld’s shows last a little over an hour, but he has about two hours of material in active rotation, so he’s able to swap in different bits on different nights. There is a contemporary vogue for turning over an entire act rapidly: tossing out jokes wholesale, starting again from zero to avoid creative stasis. Louis C.K. has made this practice nearly synonymous with black-belt stand-up. Seinfeld wants no part of it. “This ‘new hour’ nonsense — I can’t do it,” he said. “I wanna see your best work. I’m not interested in your new work.” C.K., who used to open for Seinfeld, has called him “a virtuoso — he plays it like a violin,” and the two are friendly. I asked Seinfeld if he thought C.K.’s stand-up hours, widely praised, would improve if he spent more than a year honing each one. “It’s not really fair for me to judge the way somebody else approaches it,” Seinfeld replied. “I care about a certain level of detail, but it’s personal. He would get bored of it. It’s not his way. It’s a different sensibility.” There was another big difference between the two, Seinfeld noted: “Working clean.” Almost from the beginning, Seinfeld has forsworn graphic language in his bits, dismissing it as a crutch. “Guys that can use any word they want — if I had that weapon, I’ll give you a new hour in a week,” he said.

Developing jokes as glacially as he does, Seinfeld says, allows for breakthroughs he wouldn’t reach otherwise. He gave me an example. “I had a joke: ‘Marriage is a bit of a chess game, except the board is made of flowing water and the pieces are made of smoke,’ ” he said. “This is a good joke, I love it, I’ve spent years on it. There’s a little hitch: ‘The board is made of flowing water.’ I’d always lose the audience there. Flowing water? What does he mean? And repeating ‘made of’ was hurting things. So how can I say ‘the board is made of flowing water’ without saying ‘made of’? A very small problem, but I could hear the confusion. A laugh to me is not a laugh. I see it, like at Caltech when they look at the tectonic plates. If I’m in the dark up there and I can just listen, I know exactly what’s going on. I know exactly when their attention has moved off me a little.