Hi Aaron. I'm not going to jump down your throat. I'm sure that all those components sounded better to you after they matured. I'm sure that a lot of burn in occurred.
Let's look closer in the case of a new amplifier. On one hand, you have a pretty simple electrical device that will change slightly over time. There just isn't much there that can change. On the other hand, you have the brain, which is processing the signal from the amplifier via some wire and a transducer. The brain is an extremely complex biochemical device. It is very flexible and adaptable. It shows almost constant change in how it works.
So over time, I'm willing to bet that the vast majority of burn in is occuring in the brain and only a minute amount occurs in the equipment. Notice that this doesn't invalidate your belief that the equipment sounded better over time. It's just that your brain was doing most of the changing.
My favorite case of brain burn in is the experiment where a person was given given glasses that inverted all images. The subject had to wear the glasses during all waking hours. After several days, suddenly the images that the subject saw were right side up again. The brain had burned in a bit, eh? Then the glasses were taken away. Again images were inverted to the subject. Again after several days, the brain righted the images. I have to believe that similar experiments would show the brain doing interesting processing on aural input.
-ken
Life was unlistenable out of the box!