Tina Fey arrived at “Saturday Night Live” in 1997 and toiled on the NBC landmark show for nine years. That’s a lot of all-nighters in Lorne Michaels’ office, “Weekend Update” skits, presidential sketches and opening monologues for guest hosts.

So just when she has the entire routine down pat and acts as a stabilizing force on a show that’s constantly in flux, Fey leaves 30 Rock for “30 Rock,” moving over to primetime and forcing herself to rethink everything she’s worked so hard to learn.

The writing on “SNL,” for which she earned an Emmy Award and Writers Guild Award, would have to be turned upside down for the sitcom.

“Story is the opposite of sketch,” she explains. “Here we break a story and make it interesting for 22 minutes, and sometimes we have trouble getting it down to be short enough. We often have A, B and C storylines to fit in.”

“30 Rock” opened amid decent but not stunning reviews, caught in the shadow of the Peacock’s other show-within-a-show concept, “Studio 60 on the Sunset Strip.” But just as “Studio 60” started to take on water and gasp for air, critics and audiences breathed new life into “30 Rock” as they fell for both its nuanced and slapstick comedy.

Fey admits the pilot was a different animal than the 21 episodes that followed.

“There were things that were very pilot-y in there,” she recalls of the first episode that had Fey bouncing between an out-of-control Tracy Morgan and corporate lackey Alec Baldwin. “That one you write by yourself, but then you get the luxury of working with all these other great writers.”

Growing ever more comfortable as an actress as she is a scribe, Fey learned the craft on the Second City improv stage in Chicago.

“Women are always asking themselves, ‘Should I act or am I just a writer?'” she says. “But I’m sure Ray Romano and Jerry Seinfeld aren’t questioning themselves.”

Vocation: “Writer/performer/diaper-removal expert”

Recent breakthrough: “Started crying while watching the Food Network. … Wait, did you say breakthrough or breakdown?”

Role model: Catherine O’Hara. “I grew up watching ‘SCTV.'”

Career mantra: “I have several. 1) Take it ‘Bird by Bird.’ 2) It’s a marathon, not a sprint. 3) Make hay while the sun shines.”

What’s next: “I hope I can write more movies and find a more relaxed lifestyle.”