gazing from the shadows
Nice set up!
Here's an interesting test of how air affects whiskey IN THE GLASS:
But they also say that once a bottle is opened, and especially after it is over half empty, you've got a couple months before the flavors change. That comes from the bald guy, who is, IIRC, a third level whiskey sommelier. Or something like that.
FWIW. That tracks with my experience, which is why I no longer save the last of "special bottles" for a future occasion. No, I have to finish them! Because science!
It's not that they go bad, more like they lose some notes. Easy to test your palate on this, when you have the end of a bottle that has been sitting for a while, and a fresh bottle. Do a side by side. If you don't taste a difference, then don't worry about it. If you don't care about the difference, don't worry about it. But it is an easy test.
It's a good youtube channel, so give it a shot. They range from basic to super high end rare bottles.