Remember that the thresholds crossed in November are caught in the December sweep and mailed out around the 6/7th December, arriving around the 20th. So if you cross a threshold in very early in November, get your certs just before Christmas. That means you can wait almost two months for the certs to arrive, and for the Novmeber ones, there's very little time to spend them. AC's policy is that you can only use certs that you have in hand, not the ones you've earned and are waiting for. So not only are you restricted by non-transferable certs that prevent you from borrowing from others, you can't even take advantage of the certs you have earned because of the long delivery time. I'd like to see some transparent policy on this issue, but it really is just one more (albeit more secretive) to diminish the privileges of top tier flyers.