I just made a goof. On my platinum card. In early Dec I bought a $200 united GC. no credit. I checked the platinum wiki and it recommended buying 2 $100 GCs, so I bought 2 $100 GCs. still no credit.
Jan 1, I changed my airline and bought 2 Delta seat upgrades for a friend at $99 each. Jan 4 - credit.
I was worried the GCs still didn't qualify for the credit, then it hit me!
I checked my on-line statement for the whole 2013. Guess what? I already used the 2013 credit when I opened the card!
So I'm now the proud owner of $400 worth of united GCs.