The logical conclusion from that train of thought is that the "best" tested lens will give the "best" photograph, when that is patently false. Even if you totally discount the photographer from the photograph making equation your fundamental point is flawed.
For example, you have an assignment to photograph Usain Bolt crossing the line of the 100m at the next Olympics, you can use any camera system, just get the image. For arguments sake the Canon 400 f2.8 tests better than the Nikon 400 2.8, but the Nikon has more MP and more DR, however the Canon has better AF, but the Nikon system can resolve more even though it doesn't test as well. Hm, the Canon can do more fps. Now which do you choose? The lens that esoterically "tests better" or the the other system that scores much better for more meaningful metrics; or the system that "wins" your test but for reasons other than that...........
I'm the biggest offender of refreshing my gear... I buy something with the expectation of selling it at some point in the future. I've had gear, that I wanted, for less than a week because someone made me an offer. I tend to think I'm atypical. I tend to think that some people who buy gear (and I'm not only referring to high end lenses) that they are satisfied with have the intention of keeping it well past the freshness date on the milk expires. So if you have a few thousand bucks, and you know that the half-life of a body is significantly shorter than that of a lens, you might take that into consideration.
Getting the shot now is short sided. Polaroid instamatics allowed us to get the shot now... and that really worked out well for them.