Raymond, I totally agree with your sentiments about the need to rush into buying the next step of lens as if it's a must-do, a rite of passage . Yep, new lenses with more fancy optics and faster apertures are nice, we all love that newness, but for me, the upgrade/change has to be justified.
Usually it's an overall performance reason; changing from the 18-70mm > Tammy 17-50 was purely for the faster aperture. Going from the Tammy to the Nikon 17-55 was all about build and AF speed. Opticaly there's a gnat's badger between the lenses so there was no obvious gain.
Same for my telephoto zoom. I started with a Sigma 70-200, which was a bargain and did the job grandly despite requiring a focus adjust from new. I always had a nagging doubt about whether that lens, once recailbrated, would work every time for me so in the end I swapped it for a Nikon 80-200mm. The issue of reliability was solved in an instant, whether actually happening or being a placebo effect. I use the 80-200 for some time but in the end, I craved for a bit of VR as a safety net for the lack of ultra-high ISO on my D2X. All, in all, a very sane and methodical approach to upgrade IMO.
"....It seems in this digital age we are all pulled into the trap of pixel peeping, zooming in 100% to see if every eye lash can be counted or if every freckle can be seen. I see threads like these all the time, almost always in a thread from people when they are starting out. They question the quality of their lenses. I think a lot of the time, these kind of exercise is almost an hindrance in the development of one's photographic journey. They place sharpness as the top priority when criticising a photo. If a photo is sharp then it is good. If it is not sharp then it is bad. I have never seen this kind of thinking from a professional photographer. The train of thought into critique of a photo is completely different. Not every photo needs to be crystal clear, not every photo needs to be noise free. Jose Villa is one of the world's best photographers and he shoots film. He deliberately introduce some motion blur in his evening shots because it gives them a sense of movement. So the question is why and when does change. Why does a professional think different?..."
I'm not in 100 per cent agreement with this. It's up to the photographer to assess his or her work as they want to, whether that's looking at it artistically and/or technically. I'm not a pixel peeper but I like to make sure that on the whole, there's visible sharpness. After all, I'm not paid to supply soft images as a rule although bit of blur, camera shake, whatever - it's not a massive issue if the image is smoking hot. But on the whole, sharpness does count for something when you are supplying to a client with certain execrations.
I do agree that for many beginners, starting to look at things to the enth degree can ultimately set you on the wrong path. So what if there's a minuscule amount of CA or other similar anomaly?
I won't go further into what you've written about new bodies, although it makes some sense and does match some of my thoughts (and I can't type any more)
