How often is your system "good"?

In a recent article in Stereophile, the author wrote, "When my system is good, it forces me to appreciate artists and songs I'd never noticed before."
http://www.stereophile.com/content/schiit-audio-yggdrasil-da-processor-page-2#bQow2O0DxgbPdplw.99

My presumption is that the author meant that his system sounds better some days than it does others.   I think this is an accepted fact.  I believe my system does better early in the morning and late at night due to power constraints.  I have a voltage meter on one of my outlets and I feel better about the sound when the voltage isn't sagging.  

My question for readers here is how often is your system good?   And to what do you attribute the goodness of your system from one day to the next?