The automobile "break-in" in the first 500 miles you refer to cannot be related to an audio equipment rack. Automobile "break-in" is actually a misnomer if called that. You're talking about a complicated device with fluids, many moving parts, constant maintenance, and countless other specific factors that can be directly correlated to change over time (more than 4 days I might add).
I don't know who told you about "mechanical break-in" of an audio equipment rack, but I'm all ears if this can be proven and shown translatable to an audible difference in the equipment sitting on it. The only problem is that this would be almost impossible to prove which makes me wonder how you are making such a categoric statement despite no conceivable logic behind it.
I would argue that the atmospheric pressure and humidity in you listening room 4 days apart has more to do with your system sounding different than any "mechanical break-in" of the audio rack. I could also come up with a few other more logical explanations for a perceived change in audio system performance over 4 days.
I don't know who told you about "mechanical break-in" of an audio equipment rack, but I'm all ears if this can be proven and shown translatable to an audible difference in the equipment sitting on it. The only problem is that this would be almost impossible to prove which makes me wonder how you are making such a categoric statement despite no conceivable logic behind it.
I would argue that the atmospheric pressure and humidity in you listening room 4 days apart has more to do with your system sounding different than any "mechanical break-in" of the audio rack. I could also come up with a few other more logical explanations for a perceived change in audio system performance over 4 days.