One other note. I'm sure you should plan on leaving 6-8 weeks for the certificates to arrive, but I've never had mine take anywhere near that long. For the one I just redeemed, I ordered it on Feb. 8, and received it on Feb. 17. I was worried since that was after the program switched from MBNA to BofA, but that's about the same amount of time the previous redemption took.
As far as a total per year, I think it's only 1,000 per year. I've heard of several posters who have more than one, in order to avoid maxing out annually.