However without going off topic can i ask you beazelbub what in your opinion is "too old " to start training or apply as a cadet?
I don't know. It must be subjective, and to that end there would be a very high number of possible and valid answers.
In reality, the main criteria would be economic ones. Could an individual (who had to,) recoup their likely investment over a potential return period. Does an individual feel that their ability is likely to keep pace with the steep and competitive learning curve required. Would the individuals requirements provide a fair and reasonable return to the potential employer in respect of any investment they might make.
I suspect that the laws of natural selection play a significant part in the realities of selection attrition. I doubt there are many employers that flout the regulations in respect of age discrimination, however given that it tends to become harder and more time consuming for most people to learn new skills as they naturally age, coupled with the increasing imbalance of competition from a more youthful demographic, I would suppose that the odds of success generally become lower as age increases.
As already mentioned, the natural demographic for cadets tends (as with many other vocations) to centre on the school\university leaver with an age band of 19-26, and becomes progressively lower as you deviate away from that demographic.
It is also worth bearing in mind that laws applicable in say the US or the EU, have no bearing on laws in other parts of the world. This might (and does) prevent groups of qualified pilots from moving to those areas by sole reason of their age. It may also put reverse pressure on those first and second tier jobs by very experienced pilots (in the pre-retirement phase of their careers,) moving back home from such regions
Age discrimination legislation has also served to provide very experienced pilots with significant extensions to their lifetime careers, in some cases by up to 10 years! That clearly restricts the career throughput, where pressure is taken off the top tiers. It is far more common now (than say ten or even five years ago) to see senior pilots taking part time (and full time) positions, supplemented by a pension income. At the entry level, competition is extremely intense and there is simply no shortage (or anything like it) of quality resourced applicants. For many would be career changers, the risk/reward ratios are simply too highly weighted against them to meet the normal commitments likely to be found in older candidates.
All food for thought, and as I say every case is unique. However it would be very wrong of me to suggest that something abstract and ethereal is in reality ever likely to prove advantageous.