What we need is a list of over-60 flight engineers, listed by seniority, with the date each one turns 64.
Then those guys themselves can see where they stand. If you're 62, and 150 numbers from the last guy to get a left seat, you may get the idea that you will not make it to the left seat in time to make much of a difference.
Combine that with a trip to 727 panel school and another three years of hubturning domestically, retirement may be more attractive.