When Jenn Pellegrino starts the Marine Corps Marathon, her mind isn’t going to be on whether she can finish — she’s already done 24, three in the last month.

She also won’t be focusing on time. In fact, she’s making it a point not to rush through the race.

“It’s just such a special race,” she said. “You want to soak it up. I’m just going to run with some friends and have a good time.”

The Arlingtonian will be celebrating her 30th birthday, which is coming a few days after the race.

“I felt like there’s no better way to celebrate than to do what I love,” she said.

And she certainly loves running. Those 24 marathon finishes all came in the last three years, since running Marine Corps in 2011 because she was new to D.C. and “that’s what people do.”

Never mind that she was also signed up for Philadelphia, three weeks later.

“That was what started my training strategy,” she said. “If I keep running marathons, I don’t have to retrain myself to run them the next time. It sticks with me.”

In April, she did her first two-day double — the Garmin Marathon in Olathe, Kan. And the New Jersey Marathon in Long Branch. The first went well. The second…

“I wanted to get through a few miles and see how I felt,” she said. “It got worse and worse.”

She’s joined the Marathon Maniacs running confederacy and dates a follow frequent marathoner, Chuck Engle.

“I love that no matter where you go, in a huge race with thousands of people, you have this community,” she said of the Maniacs. “There are days where I’ll be talking to another Maniac during the week and by the end of the conversation I’m buying a plane ticket and registering for a race that weekend.”

That wasn’t always her.

“When I was younger, I wasn’t athletic at all,” she said. “It started later, after college, and I did the normal progression — 5k, 10k, half marathon.”

Her mom was the runner in the family, with young Jenn tagging along on her bike. But Susan Pellegrino never ran a marathon. Until last year. The two ran Marine Corps together. Mom still talks about the race.

“She called me the other day and she ‘it’s almost the one year anniversary of our marathon,’” Jenn Pellegrino said.  “She would go for 15-miles runs and then hop on the bike, so I knew she could do it.”