Chris, I also buy bottles, some to drink and some to collect.
I only started doing this 2 months ago, so my collection is pretty boring (1975 Arbeg, 1999 bottling, 21 yr old Springbank, 20yr old Bruichladdich, Springbank Rum Finish and a couple of others).
But I hope it will be trhe beginning of a good colection (which I hope I will drink anyway)!
Anyway back to the point (oxidation), I wonder if this isn't some sort of gimmick by sellers, saying.. ..ah maybe you'll see a change in the whisky after 6 months, so you had better finish it! And when you do you can then buy another!
Just a thought.