My cockatiel, Fred, lived a few months past his 32nd birthday. The breeder started him on a basic seed mix but I managed to switch him to ZuPreem pellets after a few months. He also got a variety of fresh fruit and vegetables, plain pasta, bread, and seeds as occasional treats. In his late 20's he started refusing pellets and went back to a seed based diet, with lots of healthy supplements.
He was very healthy his whole life, other than minor respiratory infections in the autumn during his last few years. He died from accident rather than illness, getting a toe caught in a rope toy and breaking his neck in falling to the floor when he pulled loose.
I still miss my sweet old man.