Last night I finished off the GAM. When I opened it before, I only drank half of the bottle (showing more constraint than usual despite how I liked the stuff) and left the other half in the food fridge, with only the cold and the original cork stuffed most of the way back on to preserve it.
Wine does not last too long under those conditions, and I decided that I really liked the stuff, so I only waited a couple of days before drinking the rest. It actually improved over those two days. My (very unscientific) assessment of the situation is that being in the fridge for two days sealed the way it was opened it up just the right amount to let me know what it would have been like to decant for a couple of hours before drinking. The restraints were lifted up a little and it was now brimming with way more nose and taste, and all of it was good. The meatiness of the wine was accentuated nicely and the fruits were easier to taste as well.
I liked it so much I got another couple of bottles (I offered to buy a case if it was discounted further but they did not budge). I will have to save this stuff carefully – I really want to taste it after a few years of storage. This is what Penfolds means by “The Rewards of Patience”.