Ack, another question of mine that got never answered here because there was such a huge amount in a short time:
While someone told me that fruit trees don't turn pink in spring, I had asked if that was true for perfect fruit trees as well. While it hasn't happened in my town yet, I've heard that they stop giving fruit after some time and are then pretty much normal trees. Because of that, I would be interested in hearing how the game treats them in spring. Getting new trees able to turn pink this way would be way faster (and more profitable) than buying saplings, after all.
No, perfect fruit trees give perfect fruit until they die. They never become non-perfect fruit trees. At some point when you harvest the leaves will drop off and you will get two perfect + 1 rotten fruit. And a dead tree.