Thanks guys, for your comments.
Maybe my ears have been deceiving me but when I have left my hi-fi on 24/7, there did seem to be incremental improvements in sound. Now that I'm unable to leave it on all the time, my ears tell me things have deteriorated. Then again, that's probably just an aural illusion.
There's a whole oft-covered debate just waiting to happen here; regarding how we can truly quantify enhancements in sound. Like many people here I'm perpetually fascinated by the concept of "upgrading" my sound. My sceptical friend sometimes looks askance when I tell him about my latest tweak. Over the years he's had to listen to me raving about cables, interconnects, DACs, speaker & equipment stands, mains blocks et al. And to what end? Well obviously it's all about the music, or it should be. So there we sit, listening to current and past favourites (Pet Shop Boys via My Morning Jacket to Mozart). Whilst I'm certain things sound different and often "better", it's very difficult to be objective about the new audio emanating from my B&W's. And therein, I guess, lies the appeal and allure of this whole shooting match. The technical and the aesthetic bundled together.