I do think this is true. That's why I always say I can only take what I hear at the meets with a grain of salt....well, maybe a few grains lol. I think what's best is to first do your research, then go audition, and if you like what you hear, purchase it. There is no real way to avoid the disappointment if it happens but auditioning still helps. But in reality, I think a week to a month is what you need to see if it was worth it.
Auditioning is a great way to build up confidence when you are about to make the purchase, or serve as a good method of making up your mind if you are in doubt.
In the case of my buying the HD650 I was so convinced that this is what I truly wanted, that I didn't even feel the need to audition, despite the fact that there was a store selling it 300m from my home.