Does your system always sound good?

FWIW, While I don't have one of those 'incredible rigs' you refer to, I find it more a mood/music thing than the changes in the actual sonics of the system (apart from listening during warm up or if you have bad incoming juice, during the middle of the day), my systems sound is constant. But if I don't fit the piece to the mood it can be a real turn off.

Trying to enjoy a complex classical piece which requires attention, or some really up beat jazz, too early or late in the day can be a real turn off. It just doesn't sound 'musical' just sort of a lot of noise. This can be especially irritating when you know you love the music, so you tend to feel that your audio system is failing you.

This is not to say that sound cannot change due to atmospheric conditions, especially humidity, and as I mentioned the quality of your electricity (excessive RFI for example). This can make a difference but I've found if I really select a piece that matches my mood I can easily listen thru the sonics.

Well, no. I've noticed that most days it sounds great. But every once in a while after listening a while I'll realize that, in fact, it just doesn't sound as good as it usually does. It is usually about that time of realization that my wife turns to me and asks: "Does it sound as good as usual to you today?" And, we've both realized simultaneously that something is off, although nothing material in the setup has changed.
With two seperate observations of the differences it probably rules out subjective mood influences on perception. But something is different. And I don't really know what it is. Perhaps ambient temperature? Humidity? Somewhat lower voltage on the local grid? Static electric influences? Whatever it is, it makes a noticeable difference.

Yes -- as long as I don;t touch the speakers. It sounds "good" or slightly better than its "good" within the limitations of mains power and my perception (i.e. ambient noise 25-40db; moods: volatile; 3yr old: 112db, etc).
I suppose the system's own psychology comes in s/where..:)

As a rule the system sounds mediocre when you have friends over to listen to the system and often sounds suboptimum when you have friends over to listen to music. So we listen to music.:)