Absent a formal policy on extended work and flexible and phased retirement, your employer will have no stated criteria defining who can apply for what, when. Because there are employers who have designed and implemented successful initiatives along these lines, some shared standards have emerged that might provide some guidance.
By definition, it has to be a subjective decision on your part when it is time to rethink your career path. For some, there will be subtle or not so subtle hints that it might be “time for you to look around” for other options. Frequently this can happen in one’s early or late 50s – and in some industries, even earlier. The time to consider the options covered on this site is simply when internal and external signals point in that direction.
Most formal programs develop a formula for eligibility that requires a minimum age and a minimum number of years of service. A common standard is 50 years of age + at least 10 years of service. The age standard probably fits your situation.
Employers set a length of service requirement as a proxy for demonstrated value over time and potentially, the accumulation of unique knowledge and experience that companies may not want to lose. While the number of years might vary, demonstrating the underlying value is essential to have a proposal seriously considered.
In formal programs, there may be minimum expectations for performance history as captured in annual reviews. The success of your proposal will almost definitely require a strong and documented performance history. That does not mean perfect performance for twenty-five years, but in these times when increasing value is attached to proven reliability and commitment, performance matters.
With these factors in mind, the next step would be reviewing and potentially choosing one of the options outlined under “Selecting”.