Reaching back in history, a century and more, mid to large Parrots where storied to be multi-generational in their life as Companion Parrots. This based on both shorter Human life and Parrots being passed within families as from one generation to the next. All the way into the 1950 and a bit later, it was common for this group of Parrots to be longtime members of families. As Vet record keeping improved, it was common for older Vets to rely stories of multi-generational Parrots into the 1980's.
One of Parrot Forums, now less active members (henpecked) grew-up with an adult YNA that I believe to be still a member of his home. Other members have like memories.
The long life of this group of Parrots in those older days was likely greatly effected by their food intake and life style. To the point, the Parrots eat what the family eat. Which was commonly locally and/or regionally grown and consumed, and represented a wide cross-section of fresh or canned fruits and veggies, grains, seeds, nuts, and other 'home' prepared foods. Cheap seed mixes and fast-food was not part of the standard available meal.
Historical accounts of Parrots flying or whether their wings where clipped is very rare. However, stories of their active involvement in and around the home abound. That supports the point that regardless of age, they had been active.
Lastly, the International Trade dealt with older Parrots (fully fledged) only as the transportation system took weeks to months to complete and younger Parrots would not have survived.
When the International Import of Parrots into Western Europe and North America halted, so did the influx of wild caught Parrots as part of the Companion Parrot Trade. This started a very short lived approach of Long Cycle Breeding, in which the Parrot was Fully Fledged and Socialized prior to selling with an age of 6 to 12 months. Those Parrots where sold with extensive knowledge of caring for the Parrot and with in that limited market of a one days auto drive at most. As Vet records indicate, this is the last group of Parrots that have long life.
The quick change to short cycle breeding of Parrots (parrot mills) and their being sold barely on solid food and diets heavy in 'wild bird' cheap seed quickly built into place as standard practice. This followed by what is far too common today, selling of true babies still fully dependent on formula.
Long story to get to a point that around 35 +/- years ago, started the rapid fall of the expected life of Mid to Large Parrots. Today, it is not uncommon for this group of Parrots to be dying in their teens and twenties from diet and low activity induced deaths, lead by underdeveloped heart, air sack, flight muscles system and failure of organs. In addition, this group of Parrots is seen with ever increasing behavioral problems.
