IN 2004, Alex Simon and his wife, Christine, became partners in business as well as in life, starting up Las Vegas scouting agency Kids Talent Network. And that's when their joint career started seeping into all areas of their lives, even the bedroom. After grueling 16-hour days, the two would hit the sack, turn off the lights — and that "would be the time when my wife would get an idea," Simon recalls. "I'd be half-asleep and she'd be like 'Honey! I just thought about this!'"

For couples who run entrepreneurial ventures together, learning how and when to stop talking about work is critical to keeping romance — and the business — thriving. About 1.2 million husband-and-wife teams run a business together, according to the National Federation of Independent Business. Many spouses say the complementary personalities that brought them together in the first place make them compatible, trusted business partners.

Yet, the constant companionship and all-consuming work can wreak havoc on even the best of relationships. Sometimes, that results in a couple parting ways, or the business going belly-up, or both. All of which means sweethearts who launch a start-up need to recognize the dangers early on — and figure out ways to separate work and romance, says Tom Dorr, director of the Small Business Development Center at Western Washington University in Bellingham, Wash. "I've seen the potential damage that can be done if you don't manage this side of running a business," says Dorr, who has counseled a number of married business owners. "It can be really stressful, especially when the business isn't meeting expectations."

Jen Beltz and her husband, Thom Householder, make it work by splitting schedules. The couple, who have been married for almost 12 years, started Front Burner PR, a marketing firm for chefs and food companies, two years ago in Portland, Maine. They didn't realize their work obsession until a "public shaming," Beltz says. At a well-attended dinner, a chef (also a client) interrupted his discourse on wine pairings to publicly point out that the couple weren't enjoying the meal but talking about business. "Tables were turning to look at us," she says. "I tried to cover [my BlackBerry] with my wine glass."

The event served as a wake-up call, and since then the two have incorporated "flex time" to limit work hours together. Beltz's husband, an early bird, gets to the office at 7:30 a.m. and works until 4:30 p.m., while Beltz, a night owl, arrives at 10:30 a.m. and leaves at 7:30 p.m. The shifts give us "quiet, uninterrupted time to work alone," she says. They've also pledged to enjoy social outings (even when clients are present) and to keep BlackBerrys out of sight on Sundays. And often, the couple's Jack Russell terrier Charlie joins them at the office. Taking breaks to throw him a ball allows the couple to bond over something besides work, Beltz says.

Some spouses say running a home-based venture is particularly rough, especially when you're surrounded by work-related items. "We'd be jumping over boxes in the living room to get to the office," says Susan D'Aniello, who co-founded DoodyCalls, a Charlottesville, Va., pet-waste removal service, with husband Jacob as newlyweds in 2000. Eating dinner in their small house, the couple often found themselves staring at marketing materials stacked up on the table. Moving the business out of the house last year "really made work-life balance possible," Jacob says. Not only did the couple feel more free to hire administrative staff, but the separate quarters "created an immediate physical boundary between work and home," he says.

Now, the two relish the advantages of working together, which includes "having a deeper understanding of what your spouse's day is like, and being able to share in that," Susan says. And to stay on course, the two have written down their life goals — and how they hope the business will help achieve them, she says.

Dorr, who counsels married business owners at the SBDC in Washington, says writing down goals is a good exercise. He recommends that spouses jot down, individually, what each hopes to accomplish with the business — and then seeing if those goals mesh. For instance, it might be a problem if one spouse values the flexibility to have family dinners each night, while the other places far more priority on hitting revenue targets. The exercise "helps identify problems with expectations, before they arise," he says. Dorr also suggests that couples carve out "highly structured" time slots devoted to either personal life or business.

Simon, who has the Las Vegas talent agency, says he created some strict rules (which his wife agreed to follow) because he got sick of work conversations right as he was drifting off to sleep. Rule No. 1: Neither spouse is allowed to speak about the business while on the master bed — and failure to comply "puts you in the guest room," he says. Rule No. 2: Neither spouse can talk about the business at the dinner table, when the focus really should be on their two daughters, he says. Violators are subject to washing dishes by hand. "It can't be about business" all the time, he says. "You have to have that disconnect."