The first time Donna Marie Asbury stepped onstage in “Chicago” crying, “He ran into my knife — 10 times!” her daughter was in diapers.

That was 16 years ago. Daughter Jacqueline, 18, heads to college in August, but Asbury’s still playing a character named June. Along the way — over the course of more than 6,600 shows — she’s seen 20 Velma Kellys, 26 Roxie Harts and 38 Billy Flynns come and go. That she’s still here, sharing a small dressing room with four other, less seasoned “merry murderesses,” surprises even herself.

“If you asked me 10 years ago if I’d still be doing this show, I’d say, ‘Probably not,’ ” says the leggy 51-year-old. “Of course, there are days when I think, ‘Oh my God, I don’t think I can do this again!’ But then I hear [the conductor] say, ‘Five, six, seven, eight!’ and I get so excited!”

Besides, she adds, “I love seeing my 401(k) get bigger.”

Who doesn’t? Especially on Broadway, where a show can close before it opens. Asbury’s just one of the members of a small but hardy club: actors who’ve played the same role, often a minor one, for more than a decade — eight shows a week, 50 weeks a year.

Most will tell you that no performance is ever the same, that even if the actors onstage don’t change, every audience is different. And while they love the steady paycheck, they also consider doing what they do a privilege — even if it means playing a rhino’s rear, as Ron Kunene does.

“One day, I hope to play the front,” jokes the South African native, who’s been holding up his end of one of Julie Taymor’s puppet-tastic creations since “The Lion King” opened on Nov. 13, 1997. Maybe it helps that he has a few other parts, too — a tree root, a hyena and part of the trio singing “One by One.”

Granted, performing the same role in the same show for nearly 17 years isn’t for everyone. Kunene’s seen “seven or eight” rhino frontmen come and go. One of them, a former accountant, made it through just three years of “The Circle of Life” before racing back to tackle taxes.

And while the 51-year-old says he’d like to finish his Ph.D. one day, until then — hakuna matata! — “this feels like home.”

Richard Poole knows the feeling. After roving ’round the country in four companies of “Cats” and another four of “Les Misérables,” the lanky Texan was glad to hang his hat at the Majestic Theatre, where “The Phantom of the Opera” first dropped chandelier on Jan. 9, 1988.

“When I finished my 3 1/2 years with ‘Cats,’ it was my longest stint with any one company,” Poole said the other day, in his sliver of a shared dressing room high above 44th Street. “I said, ‘I’ll never do a show that long again.’ ”

Then he joined “Phantom.” That was 16 years ago. Why?

“You get a life!” says Poole, who’s played just two roles — the last eight years as the slovenly stagehand, Joseph Buquet, the Phantom’s first victim. “Where in this business do you get the chance to do simple things, like make your insurance payments or renovate a co-op?” He’s done both.

Regrets? He’s had a few. “When ‘The Producers’ happened, I wanted it so badly,” he says. But he didn’t get the part.

“One of the stage managers and I were looking out the window across the street to the St. James [Theatre] and the [‘Producers’ tickets] line was going all the way down the street. She said, ‘Trust me — we’ll still be here when that show’s gone.’ ” She was right: Raves and all, “The Producers” folded just six years later, in 2007.

I can literally play it to the day I die. I’d like to die onstage. - Richard Poole on his role in 'The Phantom of the Opera'

“There are kids coming into [‘Phantom’] now who weren’t born when it opened — our dance captain, for one,” Poole says. Even so, his own tenure seems paltry compared with that of George Lee Andrews, the show’s opera manager for 23 1/2 years. When Andrews left — to join the “Evita” revival with Ricky Martin — his son-in-law assumed the role.

“We’ll never replace George,” Poole says, fervently. “He brought it every single show! I’m just a short-termer.”

Short-termer or not, Poole’s been through a lot. He’s lost contact lenses and cracked five teeth on scenery. One time, his temporary caps landed at Carlotta the opera singer’s feet. (“They cost $2,500, so I picked them up and put them back in my mouth!”)

He says random phrases from Andrew Lloyd Webber’s deathless score still stick in his head. The other day, it was heroine Christine Daaé’s “Order your fine horses, and meet me at the door.” And while it drove him a little crazy — “We have a schematic of the Paris Opera House here, and I’m thinking, ‘Where do they keep the horses?’” — he has no plans to leave.

“This role isn’t age-restrictive,” he says. “I can literally play it to the day I die. Have you seen [the Majestic’s] stagehands? They’ve been here for the entire run and they’ll do it till they fall over, so why can’t I? I’d like to die onstage.”

Sixteen years into “Chicago,” Asbury feels differently. “I’d like to do this show 20 years and then walk away. I’d say, ‘I was able to do this, physically and mentally, for 20 years!’ and give myself a hug.”

Until then, she’s determined to keep her focus — no matter how many times she’s heard that repeated refrain “the gun! the gun! the gun!” (“I think my brain is used to it”). Granted, it doesn’t help that her husband, actor Cleve Asbury, played a small role in the 2002 “Chicago” movie, which their daughter likes to screen for friends.

“I’ll walk in and say, ‘Really? Do I have to hear this now? Because I’m going into the show in two hours!’ ”

Luckily, she says, this being live theater, every show she’s in is different. And not only has she occasionally gone on as the leads — the high-stepping Velma and, more recently, jail-ruler Matron “Mama” Morton — she’s seen a veritable who’s who of actors waltz in and out.

“Taye Diggs was an amazing Billy Flynn, and so much fun to look at every night,” she says. “When Rita Wilson did the show, Steven Spielberg came three times and was at her closing-night party. I got to meet Tom Hanks!” And George Hamilton used to hold court backstage, she says, telling stories about Elizabeth Taylor and old-time Hollywood.

“The great thing about ‘Chicago’ is you get to say murderous things and then you go home and you’re happy,” she says. “I can leave the show at the theater when I come home to my family and dog. I feel blessed!”