Fearful of losing skilled workers,  some companies are looking to hold on to baby boomers who are either nearing or have already reached retirement age. Winning strategy or just delaying the inevitable?

By Gary M. Stern, contributor

FORTUNE -- The long-awaited retirement of the hordes of 76 million baby boomers born between 1945 and 1964 has begun.  But some employees aren't ready to say goodbye to their cubicles or labs, and some companies don't want to lose valuable employees. The golf cart, cabanas, and sun tan lotion may just have to wait.

In 1985, 10.8% of people over 65 worked full-time or part-time. By 2011, that figure rose to over 18%, according to the AARP Public Policy Institute.

Baby boomers who decide to leave the workforce offer an opportunity for younger staffers to move up in the ranks. But at pharmaceutical, technology and engineering companies, losing experienced employees can lead to a thinning of human resources, or brain drain.

In a recent AARP survey of 1,000 human resources directors, 69% said that their companies are looking to keep older workers as part-time workers and consultants and 46% are trying to entice older workers to stay as full-time employees.

Keeping baby boomers on staff has its drawbacks as well. This strategy can "delay younger workers from moving up into upper-management level jobs and delay their development as leaders. It creates a bottleneck in these organizations," explains Peter Rodriguez, an associate professor of economics at University of Virginia's Darden School of Business.

Abbott Laboratories (ABT), based in Abbott Park, Ill., introduced a "Freedom to Work" program in 2008 with the goal of retaining staff members 55 years and older with 10 years experience to ease the negative effects of a retirement exodus. Every year, 200 Abbott employees, from sales reps to IT staff to research scientists, participate in the program, and they receive full benefits and adjusted pay, explains Lesli Morasco, director of benefits at Abbott.

Abbott staff can opt to work four days a week or managers can return to work on a more relaxed schedule, says Morasco. Employees who participate in the program have the option of mentoring and training other staff members or continuing to work on projects. More