I was able to just clear the threshold for my latest DL Amex miles boost after the Dec. closing date and before 12/31, to ensure (I hope) that the 10,000 MQMs apply to my 2008 status. But I made it with $25,036 in spending. Now I have a few gifts and such to return after Christmas, and some of those were purchased with the credit card in question. If I have $50 worth of returns, say, on Jan 2, 2008, is it possible/likely that the refund would go on the card and cancel a $50 purchase in 2007 and thus bring my total 2007 spending back below the threshold (and thus lose me the miles boost), even though the refund is credited in 2008?

I'm not going to take any chances with this, but I thought I should post it as a possibility in case anyone else might be in this position and might want to consider the possible danger.