rmcdonal: I appreciate what you say and as a Flight Instructor myself I can relate to the example you gave.
However at PPL level, many of the older students are either: Not persuing an airline job and are doing it for the "challenge", or have other factors to balance like existing careers and families, which intrude on the amount of commitment they can give at this level.
By the time an older pilot has attained his / her CPL/IR their priorities are the same as everyone else's. Get a job!
This puts a completely different emphasis on their motivational differences and constraints - which as you will know from teaching theory are the major influences on learning performance.
Of the more mature students I have taught or flown with who are aiming for an airline career, I would honestly say that on average they are equally motivated and just as capable as their younger counterparts and there is little to choose between them.
The point which I try to keep repeating is that older pilots need the same opportunities to apply for jobs and job related training as younger pilots. When it comes to interview and selection, then each person must be selected on their own merits and performance - not on some perceived generalisation such as purely their age.
LD Max