Why no “Break in” period?

I don't know about line conditioners. I have A PS Audio power regenerator. I do not think it needs to be "broken in" (whatever that actually means with parts that dont move) because it takes ac power from the wall, converts it to DC, then regenerates a new unclipped sine wave. I think of it as an on/off switch you either have clean new power or you dont. I dont see how a reconstructed sine wave can get broken in. I am a degreed mechanical engineer and I have taken classes in heat, sound, and light. I am very skeptical of things that cannot be measured such as break in. I buy in on the idea of say an engine in a car because it has moving parts that have intimate contact at very high forces. I think it would be foolish to believe nothing would change with time under those circumstances.  I noticed a huge difference after installing the power regenerator, but I had huge line noise prior. The noise I had was like a drum stick hitting a rotating fan blade. You did not need to be an audiophile to hear it, for a while I thought I blew a speaker. The regenerator completely fixed the problem.

All this talk makes me laugh. Has anyone here been to an audiologist ("hearing doctor") I doubt it. If you do go to one, you will probably learn that your ears and your hearing are basically no different than anyone else around your age. A few will have a little poorer hearing and some will have a little better but none will hear outside the realm of human hearing, like bats and dogs. I worked st a Detroiy auto plant. All employees had to take a hearing test every 6 months,  no ex exceptions. Almost all came back normal.

People that claim they hear things that others dont are probably confusing familiarity with sensitivity. For example if you hear something once or twice a day for years and then one day it slightly changes, that is familiarity, not sensitivty.

The most objective test of hearing that I have witnessed was a test administered by a Proffessor of Music at at a university niversity in NY who is an instructor of guitar. He took a student that has perfect pitch (been tested) and had her favorite songs (she was familiar with) played through high end headphones and tried to distinguish between vinyl and CD. She failed, her percent of correct responses was no higher than the success rate of someone who guesses without even listening.  The test was not exhaustive, I would have done it differently, but it did convince me that those that claim they hear what others dont, are wrong. I think Mr. Carbon is confusing familiarity with sensitivity. For those Interested, the test was published by Rock Beato on YouTube so you can watch it yourself and come to your own conclusions.