Also peoples neurological systems do not stay totally constant over time so there is always the possibility that a change heard has nothing to do with the gear.
Then there is the weather and humidity and barometric pressure that are also changing all the time and might effect fine details of what one hears.
So its very hard to reliably attribute a change over the longer term to any one thing.
All you know for sure and that matters is if it tends to sound better, worse or the same to you over time. Someone else in the exact same boat could easily reach a different conclusion.
Then there is the weather and humidity and barometric pressure that are also changing all the time and might effect fine details of what one hears.
So its very hard to reliably attribute a change over the longer term to any one thing.
All you know for sure and that matters is if it tends to sound better, worse or the same to you over time. Someone else in the exact same boat could easily reach a different conclusion.