Winemakers tend to (In my opinion) err on the side of caution. We sanitize, we add Kmeta to fresh fruit regardless if it needs it or not. These are all conservative approaches. Taking a stave out of a ferment, freezing it (in a baggie?), putting it back in the wine confuses me, but it’s “probably” ok. Why not just leave it in to begin with, but that’s your call. Oak gives up it’s flavors over time, at some point it is expended. Once used it may not give any flavor after a few months, but I don’t know that number. 12 months in the wine, I’m guessing it has no flavor left to give.
Compared to your time and effort, sanitizing is cheap and effective. Reusing staves is cheap but may not be effective. Using brand new staves for every application is cheap and effective. Tossing a batch because it got bacteria isn’t cheap or sustainable. I’ll bet your freezer isn’t sanitary. Take out the last item from way in the back and see if there are crumbs/dust in the freezer tray. Those particles are on your staves unless you took precautions.
Being a good winemaker sometimes means having a little OCD is a good thing. But don’t stifle your creativity, just be aware of the risks.
