Good points @sfseay and Geoffkait....
No, I have not sat on my thumbs for thousands of hours, but yes, I typically assess the sound periodically on a number of CDs, particularly on a test CD containing several key tracks that I compiled in 2005. Yep, still use the same one for consistency, amongst other ones.
I also have developed an automated spreadsheet tracker that I have used for a decade or so to track and annotate progress.
When possible, I drive a music signal or FM instation hash through the system whenever I am not listening to music... Yes, this means also night time.... If not FM radio is available.... Like in my current setup, I play music at low level or a break-in CD containing hash.
If the weather is stormy, I disconnect the entire system from the AC mains.
I am sure that time of day, weather, AC mains load all play a part on any particular data point.... However, if the long term trend looks like a stockastic curve pointing upwards, I venture to guess that things are moving in the right direction.
And you guys are correct..... Do not trust me nor anyelse's ears, no matter their particular metallurgy.... Golden, Silver, Tin, Transuranic, leadden, or otherwise.... Use your own ears as much as you can, and well... Yes... Trust them... It's your musical taste that counts, not mine. If you do not, you will turn into a paper audiophile.
G.