When their daughter Leslie went off to college last year, Hal and Sharon Eisenstein followed the path of many "empty nesters" these days by reorganizing their lives. They purchased a new four-bedroom home in the Shores, a Kenco Communities development in West Boca Raton.

"The fact of our daughter leaving, prompted us to try something new in our life," said Hal Eisenstein, 44, a partner in South Coast Painting & Waterproofing, Boca Raton. "We wanted to stay in the Boca area, but didn't want to stay in the same house. We're already looking ahead to retirement and we'll probably stay right here. You look at the cleanliness, the shopping, the sports and theaters, and you say, 'this isn't so bad.'"

The Eisensteins typify the empty nesters who have helped fuel Florida's real estate boom. But the signs are that this market is changing. For while the number of nesters continues to increase, their spending on Florida nesting places does not.

In their report, "An Overview of Demographic Trends and Housing Market Impacts: 1995-2000," published by the Fannie Mae (Federal National Mortgage Association) Office of Housing Research, researchers Isaac Megbolugbe and Patrick Simmons project the greatest household growth will occur among 45- to 64-year-old single persons, and married couples without children younger than 18.

In Florida, the 45 to 54 age bracket is the fastest-growing segment. By the year 2000, Florida will have 2.091 million residents in this age bracket, a 58% increase from 1990 to 2000, according to James W. Hughes, Rutgers University professor and author of "Clashing Demographics: Homeownership and Affordability Dilemmas."

Pre-retirees from the Northeast and Midwest typically have purchased second homes and vacation units, testing the waters before retiring here full time. Middle-aged Florida residents traditionally considered trading down in square footage and up in amenities, fueling demand for waterfront or golf course community homes. In recent years, Latin American and European empty nesters have formed a significant segment of the luxury condominium market in South Florida, Orlando and Tampa.

Megbolugbe and Simmons note that about half of all second-home owners are in the 45-64 age bracket, 80% are married and 70% have no minor children.

Yet, despite the demographic upsurge, demand from empty nesters is well below expectations. The children are leaving home, but the parents are staying put -- forgoing the pleasures of a new home or a new community. The result is troubling to the state's real estate developers and builders.

There are a number of reasons why the real estate market for 45- to 64-year-olds is softer today than in the past:

Empty nesters are under more financial stress. Theirs is the "sandwich generation," caught between demands to help their children financially and their aging parents.

Today's empty nesters feel more insecure than their predecessors. Two leading concerns are the future of Social Security and health care.

Corporate consolidations and downsizing have reduced empty nesters' current income and lowered their pension expectations.

More 45- to 64-year-olds are choosing locations other than Florida. Fast-growing towns in the Carolinas, Colorado, Montana and other Western states are attracting more pre-retirement buyers.

Although empty nesters are generally at the peak of their earning years, they are buying more conservatively than before. Concerned about their long-term financial situation, many are "under-buying," purchasing more modest homes than in the past.

Slower housing sales in the Northeast over the past few years have reduced the traditional pre-retirement migration pattern to Florida.

Lower real estate appreciation rates mean many empty nesters lack the equity to buy a more expensive home. They may opt for a moderately priced house or condo, or simply decide to stay where they are now. In his study, Hughes says the 1990s could be the decade of the "frustrated trade-up buyer" who may upgrade an existing home, instead of buying a new residence.

Lower appreciation also lessens the desirability of purchasing a pre-retirement or second home as a long-term investment. This lack of investment demand is one of the key factors holding back the second home and vacation unit markets.

The bottom line: Many empty nesters are holding their "be good to myself" money in reserve, reluctant to buy new primary, secondary or vacation homes.

"In the mid '80s, today's empty nesters were working and had kids at home to support," says Ken Endelson, chairman, Kenco Communities, based in Boca Raton. "They thought there was nowhere to go but up. The recession of the early '90s caused many of them to re-evaluate their financial situation and how hard they were willing to work."

Endelson's Palm Beach County projects, Addison Reserve, Wycliffe Golf & Country Club and the Shores, typically attract empty nesters, with their active amenities and clubhouse atmosphere. But Endelson said the current group of buyers is focused as much on value as anything else. "They want to be sure they can afford a certain lifestyle as they get older," he says. "They don't want to have an expensive albatross over their heads. To succeed in today's market, you need to provide a quality lifestyle that's affordable."

For Endelson, that means providing a full package of active recreational amenities -- golf, tennis, fitness centers, olympic-size pools -- with new homes in the $200,000 to $700,000 price range. "You also have to design the homes efficiently, with practical space, so they can make the best use of the home. It's also important to have enough available bedrooms, so their children can visit them."

Endelson, like other Florida builders, has tailored his projects to appeal to middle-aged couples with tighter purse strings. "For empty nesters to change their lifestyle, they want to be sure they're improving their situation," Endelson says. "The community and the amenities must be perceived as clearly superior to their existing situation."

At this point, it's clear that the empty nester demographic segment has great potential importance to Florida. But turning this potential market into actual sales will depend on how well the state's builders and developers can see through the eyes of these often insecure middle-aged consumers.

Contributing Editor Lewis M. Goodkin is president of Miami-based Goodkin Research Corp.