I think part of your suggestion is: Establish a baseline early on. Kind of like a cardiologist or X-Rays!
Once I know my lens is performing as it should, I save my Reikan FoCal charts for my micro adjusting, aperture and AF performance. Also like you, ISO chart shots so I can judge performance at a glance if I suspect something is amiss.

Regardless of the care you take, things wear out even without use. Especially with the use of so many plastic parts now, and so many crazy things in the environment. How many of us have witnessed plastics yellowing or their compositions changing even in a darkened closet? I would think with the insanely high tolerances necessary in modern optics, the slightest degradation of any element inside a lens could cause a significant change in IQ.

But without establishing those charts early on, you could very well wind up second guessing yourself and maybe never do anything about it. As we see, it's a pretty painless process and I'm glad Canon promptly solved the issue.