Guess I'm definitely in the minority here and think it's a horrible idea for reasons almost too numerous to list. It definitely goes against what I've observed in 35+ years of listening not too mention know about biology, neurobiology, anatomy, etc.. It seems to me this method is a surefire way to disaster and picking some bad gear and miss good gear this way very easily. One might as well toss a coin.
As for Mark's example, it's really an anecdotal example and there's so many things that could be amiss other than the equipment. This component is exciting a room issue you didn't know existed. There's some sort of interaction going on between the components that needs to be sorted out. The equipment has to be properly warmed up. To wit, every tube amplifier I've ever listened to needs a minimum of 30-60 mins to sounds its best and if it uses interstage coupling transformers like the VAC Rennaissance or Audio Note amplifier do/did, it could take 3-4 hours to sound their best. And forget it for digital and solid-state gear. Unless their on for a day, listening is pointless (as are electrostatic speakers for that matter).
Then let's look at the underlying and accompanying biology, physiology and neurobiology.
1. Do you think your hearing is the same every day?
2. Do you think your system sounds the same every day?
3. Let's consider the process of adaptation? Our bodies adapt/get used to various stressors with time that actually occurs via genes turning on and off. Common stressors? Heat, cold, alcohol, noise, music, etc. Usually as shown by Selye, adaption takes a minimum of two weeks and can continue for up to 7 weeks or so. So if I put you in the Arctic, you'll shiver for a couple of weeks but eventually you'll adapt and get used to the temperatures. Same goes for hear and that process is mediated via heat shock proteins.
4. What about the various receptor in our bodies? One is sadly mistaken if you think that we experience music only through our hearing. Our body is covered with receptors in the skin, etc. almost too numerous to list that sense pressure, pain, etc. They clearly play a role in our response to music. Remember not everything that goes on in our brain is consciously processed.
5. Then there's the issue of how the brain perceives music. I strongly urge everyone if you haven't yet, pick up a copy of the New York Times best seller This is Your Brain on Music, vol. 1 and 2. A very educational look at why music is so important to us and how and why our brain responds the way written by someone who is among other things, a musician, producer and neuroscientist. You should also check your preconceptions at the door since his research overturns many myths and dogma that dog the field. (don't forget how we react to music can also be traced to our exposure at young ages.)
But it's even more important to understand how our brain works and its dual nature. Basically we can break our brain down into the primitive/limbic system that evolutionary we've had lots of experience with for millions of years. (one --of many--books that goes into the science and psychology of our brain is another Times bestseller The Happiness Hypothesis written by Jonathan Haider.) Then we have the more recent on the evolutionary scale frontal cortex part of the brain that we're starting to figure out how to use. What happens is that our "early" response is determined by the primitive brain eg. fight or flight responses. But over time, our frontal cortex become more involved in the processing (I could spend quite a bit of time talking about brain processing and how depending on short term memory is about the most unreliable thing because if its limited "disc" space and parallel processing that leads to lots of bottlenecks and slowing down of processing.
(Here is also a good list of book on our brain and musical processing, etc.
7 Essential Books on Music, Emotion, and the Brain | Brain Pickings
So in the end, short term decisions in my experience not only are bad but are totally opposite of what I've observed. In fact, in general I've found that equipment that has sounded good initially quite often wears thin with extended listening (eg. this is the primitive brain talking to us and looking for spatial cues, exaggerated high frequencies and things related to flight or fight.). Conversely, I find that gear that often sounds bad or not much different will sound better with extended listening (even after breaking in).
As they say YMMV....
