The question I really have is the PIA recalculated each additional working year beyond 62 based on that year's new bend points, or are the age 62 bend points used (with the new AIME, if changed, in both cases)?
An attempt to answer my own question is based here: http://www.ssa.gov/oact/cola/piaformula.html
My understanding from this page is that, yes, I always use the age 62 bend points.
This page says
PIA formula bend points
The PIA is the sum of three separate percentages of portions of average indexed monthly earnings. The portions depend on the year in which a worker attains age 62, becomes disabled before age 62, or dies before attaining age 62.