With better health and greater longevity people over the former retirement age are generally still able to remain busy, useful and competent to work. An arbitrary cut-off age of, say, 65 for men and 60 for women is no longer necessary or relevant.
Had there been a retirement age in the days of the Bible, history would have been totally different, and Moshe Rabbenu would never have even begun his great life’s work.
How, then, can the Torah insist on a Levite retiring at 50, as is laid down in today’s sidra? “From 30 years old and upward up to 50 years old” – a span of no more than 20 years – is the length of a Levite’s career in the sanctuary (Num. 4:3).
But there is a reason. As Rashi and Ibn Ezra point out, the Levites were engaged in physical work, especially carrying the equipment of the tabernacle, and this required them to be in peak physical condition. Had their work been less strenuous, no retirement age might have been necessary.
Hence the issue that has to be addressed in a later generation is whether the particular person can still do the particular job after reaching a certain age. If they can there should be no automatic expectation that the moment they turn 65, for instance, they should step down.