Love getting new equipment, hate the break-in

Another benefit for me in using ss gear, is the "always broken in", as I leave my gear on / music playing, 24/7, unless I am away. 

@oberoniaomnia...... Perhaps I was a little hasty there.  Yes, there may be no stats to back this up, but it definately is something I hear.  Makes you wonder if the new product is actually an upgrade.  And then one day it's broken in and everything is all right again.  

@oberoniaomnia +1/-1 on this one: "I challenge anybody to do a blind A-B test with a burnt-in component vs out of the box”.

The biggest problem is a manufacturing variations, including all components and fully assembled units. ALL products are not equal at any measurable or listened performance metrics, at the end of production line, aging also hits devices differently, due to many factors, temperature/humidity etc. 

Any time I read about device A compared to device B, the key question is, what is the condition of DUTs (device under test, maintenance, calibration, etc)?

@westcoataudiophile That is referred to as "within sample variance" in statistics. Easy to deal with by increasing sample size. One can start with n = 1 for each sample, aka a pilot study. If there is some reason to believe that there is something to it, then increase sample size. Basic experimental design. In rare cases where sample size cannot be increased, there is the approach of assuming z-normalized variance from better known sample and assign that variance also to the n = 1 sample (Sokal & Rohlf: t-test of single observation with a mean).

With SS, as a gut feeling (no data, not an electrical engineer) I doubt there is much variance these days. Consider also that reviewers only listen to one copy of the component under review. While I have heard lots of disclaimer "in this system" "in this room" "to my ears", I have never heard "this particular box". There have been some reviews out there where reviewers found errors/bad components of various flavors, but fully functional units are generally considered to be identical. That is again based on statistical principle of null hypothesis = no difference.

@boxcarman I don't doubt that you hear something, which is entirely subjective. What I suggest is that your hearing/brain auditory processing adjusts, while the component is not changing at all. Habituation is a well-known phenomenon, e.g., with fountain noise that first is noticeable, even irritating, then fades into background.

@ober..:  "fully functional units are generally considered to be identical"

not in real design/production/service flow, where often “the same looking devices” have the designator components from different suppliers, design change almost every day, test equipment introduces additional tuning variations and so on..