"While I was appreciating the fact that he was being more 'normal,'" she says, "I was replaying the previous six or seven years, and just waiting for the other shoe to drop. I was quite tense. I couldn't sleep because of back pain. I wasn't allowed to talk to him about what went before -- those were things like infidelity."
Then she found condoms, which the two don't use, stuffed inside a sock. "To me, that was a conversation starter," she says. "It almost seemed like he was trying to put something out there -- either he has a dedicated lover on the side ... or he's open to hookups, or sending me a message to back off."
Once they begin, these cyclical patterns can be tough to break, says Roland Hinds, the host of TruVue Relationship Radio in Los Angeles and author of "Are You the Right One for Me?" Although Hinds, 45, counsels others on how to end destructive relationships, he doesn't hesitate to admit he's had his own share of them himself.
"I dated a woman on and off for two years," he says. "Her initial pattern was to become emotional and combative when she became deprived of attention. She always felt she was competing with my clients." So he stopped speaking to her for months. Then came her phone call from out of the blue, and they were back on. "She apologized and assured me things would be different."
Within months of their getting back together, "she returned to default with a vengeance," says Hinds. "It was like working overtime in my relationship. I had to be firm and sever all ties and tell her we shouldn't contact each other again, ever. I think she thought I was joking at first. I told her I would not accept her calls, nor answer any texts."
"You can pretty much stalk someone by sitting in front of your computer," says Alpert, the New York therapist. "In the old days, you would do a drive-by their house on a Friday night and see if the light is on, oh, they're home. But Facebook has become today's version of a drive-by. You know if they're dating someone, you know if they're out. If they're vacationing you see the pictures. There's just no escaping."
Which only adds to the ambiguity as to whether a couple has actually split up. "They declare a breakup, but then they have continued contact," says University of Texas researcher Dailey, who studies the breakup strategies of the on-offs. "It's this reluctance to stop contact with the person. They strategically kind of leave the door open, whether it's conscious or not."
Sometimes it's a sunk-cost fallacy that keeps the cyclicals from quitting. "Because you've put so many years in, you're afraid to walk away, and you're just going to continue putting years in," Sarah says. "I took him on as a project. He would be a prize when I brushed him off."
But people are only capable of so much "remodeling," something Atlanta native Aimee, 34 -- who also asked to keep her full name out of this -- realizes as she muses on her own seven-year/five-breakup roller coaster ride of a romance that began at a gas station. "Each feels the other needs to change," she says. "He lives in a box. He won't go anywhere. He doesn't have a romantic bone in his body. He's a neat freak," she says of her boyfriend. "Buying me flowers because I complain I never get them? That's not going to work for me. I want flowers without my mentioning that he never does anything romantic," she says.
"I'm tired of being a girlfriend. Unless I'm getting a ring, I don't want to be with him," she says. "It's either a ring or nothing."
Aimee might want to hold off on that marriage ultimatum. Eternal boomerangers who've broken up and renewed a couple of times are more likely to separate, or divorce, say researchers.
"You see that breaking up is an option," says Dailey. "You have the pattern of getting out of the relationship."