I must take issue with the apparent stated premise that people over a certain age (whatever that may be) should not consider taking up GA piloting as a hobby. What evidence is there to support this suggestion?
The number of newspaper/BBC reports of elderly driver wiping themselves out (or coming close to it) driving the wrong way down the motorway.
The number of AAIB reports of elderly pilots pranging their aeroplanes on take off or landing, where there are no external factors, nor mechanical failure.
Insurance companies who refuse to insure > age 75, or impose special conditions, which is obviously a consequence of historical analysis and risk assessment.