Ad honcho Charlie Rutman is on a conference call with his executive assistant Connie Gaspe. They bicker, joke, interrupt, and finish each other’s sentences like an old married couple. In fact, they are married—professionally speaking—and have been for the past 24 years through a succession of steps along Madison Avenue. For him, each new company was an opportunity to move up the corporate ladder; for her, the choice was to move with him or swap bosses. On each occasion, she decided to stick around, and Rutman has proven that he was worth tying her fortunes to as he’s risen up the corporate ranks.

Few business relationships are as close as the one between an executive assistant and his or her boss. In fact, the working relationship involves more time spent together than the average husband and wife. Executive assistants become familiar with the intimate details of their bosses’ lives—weddings and divorces, kids’ graduations, medical histories, etc.—some even become an extended member of the family. Rutman says Gaspe and his wife often talk to each other on the phone. It’s no surprise, then, that many executive assistants follow their bosses from job to job and that some wind up staying with them for decades.

Oftentimes, executives and their assistants are fiercely loyal to one another. In Rutman and Gaspe’s case, the two started working together in the early eighties at ad agency Backer Spielvogel Bates, when Rutman was a media supervisor. After 14 years there, he received an offer from a rival agency, DMB&B, and was initially told he couldn’t take her with him. “There was a series of circumstances: Someone left, I got promoted, and Connie and I got reconnected.”

Each time Rutman moved, he negotiated for his trusted partner to move, too, as part of a package deal. Rather than becoming anxious about the change, she was the one urging him to accept each change. “He’d come in and say, ‘We’re gonna move together,’ and there was never any question I wouldn’t go,” she says, “I’d say, ‘As long as you’re comfortable, I’m right there with you.’ ” The downside, though, has been having to leave behind friends she’s made at each stop along the way.

Another executive assistant, who didn’t want to use her name because she wasn’t authorized to speak by her boss, explains why such partnerships endure. “With any new job, it’s 50 percent about the boss and 50 percent about learning a new company; this way only one-half is new,” she says.

Some executives are so tied to their assistants, they couldn’t leave them, even when they’re out of work. Before Brian Sullivan became C.E.O. of recruitment firm CT Partners, he wasn’t employed for two years. But he didn’t want to lose Patricia Kissane, his assistant when he was at Heidrick and Struggles, so he paid her out of his own pocket. It was a good move for Kissane, who kept her income and went on to assist a C.E.O.

While attaching oneself to a rising star can be great for one’s career and paycheck, the practice also carries risks. Bosses get fired or retire unexpectedly, sometimes leaving the executive assistant with the option of perhaps working in a different department or leaving the firm altogether.