I think what happens (and it has happened to me) is that we are initally so excited about the positive aspects of a new headphone ( and how they "fix" the problems of the previous one) that we overlook the negative ones. They catch up to us later on. Then we long for something "better". Thank God our spouse/partner is not a pair of headphones.
Yes, the result of a lack of perspective. For example, I'm quite interested in the Earsonics SM3. It's a $400 universal earphone that appears to be very promising. However, the only comparisons have been to lower-priced universals. Nobody who's reviewed it seems to be familiar with the lower-end customs of the same price (UE4, JH5). So how can I take those reviews seriously?
For the LCD-2, I think what's mostly lacking is more experience with the HE-6. But I think Fang recognizes this, and is taking steps.