Hmmm, I seriously doubt anybody actually vets 100% -at least, I never met anybody and I am sure that rescues don't do it because it would cost around $500 for each bird - plus some of the tests are not always 100% accurate [they give false positives and negatives]. I mean, do you know anybody who runs a PDD test on a bird that acts and looks healthy? I don't.
As to age and energy level - there is no difference in energy level between a young and an old bird. It's a common misconception, though... I've heard many times people saying that this or that bird has no energy "because it's old" when the problem was not age but health issues. The thing with birds is that they are not like mammals. Mammals age the way we think of aging, the way humans age: hair changes color and texture, fat deposits in places where it never did before, muscles deteriorate, teeth become worn out, we lose the ability to procreate, etc. but Nature did not 'design' birds that way and that's why nobody can tell how old a parrot is unless we have the leg band with the year it was hatched. Old birds look and act the same as young birds. Sheesh! Birds can even produce offspring and raise it successfully when they are ancient! Look up this story of a bird that was still producing birds at 66 years of age when we used to think that the average lifespan of her species was only 40!
https://news.nationalgeographic.com/201 ... ss-laysan/And they don't care, either. I have a 36 or 37 year old female amazon whose husband must be in his late teens if he is that old! Some cougar, eh?