A manager is concerned about retaining a top-performing employee who is 48 years old. The employee is highly skilled but seems disengaged and has been with the company for five years. The manager recently offered a significant salary increase, but the employee's motivation did not improve. Based on common workplace characteristics of individuals in this age cohort, what is the most effective strategy the manager could use to improve the employee's motivation and increase the likelihood of retaining them? Explain your reasoning.