There is no way my brain is retaining what I previously heard and then comparing it to what I currently hear.
@dwcda correct. And this has been demonstrated to take less time than many audio gurus assume. If comparisons are not a literal flip-switch, subjects can be quick to lose, alter or invent, context. A “trust your ears” stance is necessarily deaf to this ubiquitous limitation, and I think that’s fine so long as the choice is not professed to be useful for everyone’s case.
The alternative is to connect all of the new cables, listen for a week or so & then switch back & see if you feel you’re missing anything. But then your brain takes over & your biases will have as much impact as any potential change in sound quality.
That’s not an alternative, it’s a totally different (and perhaps even less-controlled) test that will probably give inconclusive results. The second part, you’re surely accurate.
So I’m stumped as to how to proceed.
There are options, but they require designs using repeated measures and those won’t do well with a sample size of one (listener). By virtue of how such comparisons have to work to be analytically robust, one person listening for preference differences is a non-starter.
Situations like these, some folks will decide on alternative assessments that aren’t controlled. And for some folks, that’s good enough (and again, I agree fine, if they’re not processing it to be suitable as a rule). If one cable or three cables or all cables make a difference to your perception, whatever kinds of tests you have or have not done, the query for you is: How much difference should be perceived for said device(s) to be worthy of inclusion / purchase?