I suspect the upgrades for most of us won't end until we age out. I know I'm done building my last system, I have nothing to complain about as to sound quality, no reason to start over.
My sense is once you've settled on amp, preamp and speakers you're in good place. Sources and tuning are enough to keep one occupied, and having settled on vast majority of inherent sound qualities playing at the margins completely satisfying. Optimizing my streaming has totally reinvigorated my interest in discovery and experimentation. At some point this too will be settled, already have plans for vinyl side upgrades.
I suppose if one's into modding and tuning there's never an end point, system value has no bearing on this. Again, it will likely be age or death that imposes static system on me.