Last year, Mary Schellhammer and her husband Paul left behind their Spotsylvania, Va., personal-chef business and took an extended summer vacation  in Europe. Next year, they're planning a two-week trip to Alaska.

"We try to do a big trip every two years," Schellhammer said. During the off years, they travel around the country for weeks at a time in an RV.

Yet, for most U.S. small-business owners -- and Americans in general -- that kind of vacation time is becoming increasingly rare, recent surveys show.

Less than two-thirds of the nation's small businesses owners planned to take at least a full week away from work  this summer, according to an OPEN from American Express survey of 600 businesses with fewer than 100 employees. This spring, a full 60% of U.S. consumers said they had no vacation plans over the next six months, according to the Conference Board.

Americans also tend to take much shorter vacations -- just 13 days on average -- compared to the rest of the world, the World Tourism Organization reports. That's less than half the average number of vacations days in Japan, Canada, Britain, France, and Italy, according to the agency.
 
So why are so few U.S. business owners taking time off? Nearly half of the owners surveyed by American Express said they were worried an important client or customer would receive bad service while they were away.

Of those that planned on taking summer vacations, a full 54% said they would check with their business at least once a day, compared to 25% who said they wouldn't, the survey found.

"Business owners tend to take on all or most of the responsibility for running their firms," said Susan Sobbott, the president of OPEN from American Express. "Given their concerns about the state of their companies while they are away, many find it impossible to truly disengage from their business during a vacation."

Instead, the survey found, many entrepreneurs try to mix business with pleasure, though the rates vary by gender and size of business. A full 38% of women business owners said they combine work with their vacations, compared to 27% of men, the survey showed. In addition, owners who run smaller firms -- those that make less than $200,000 in annual revenue -- are also more likely to take working vacations, the study found.

To make the most of a vacation, Alice Bredin, a small-business consultant for OPEN, suggests owners give key clients a "heads-up" before leaving, or try to schedule trips during business downtimes.

Those who simply can't get away this summer should try to reward themselves with other downtimes, such as a going to a museum or a ballgame, or trying out a new restaurant, Bredin said.