I tried using expired rum in past and it worked fine, it might be similar to potions from MT.
Looks like before releasing new set, old potions are removed from everyone's inventory/estates as the potions link is same.
I'm assuming that potions from 44th MT were present in inventory before start of 45th MT (10 Oct), so it might have worked if used between 1st Oct till 9th Oct.
On same note, the rum in my inventory expires at 1 Nov so I wonder if we can expect another pirate raid in Nov. |