We purchase them and stock pile them and the only reason I mail them certified is I like receiving them by mail and use the card envelopes to put tip money in them. Also this year I put them in gift boxes and wrapped them for my fiance' for Christmas.
I buy them for the simple reason I like to have everything paid for ahead of time like I said in an earlier post. You save nothing buying them just peace of mind that you are paid in full for your on board credit when you apply them ahead of time.
Inspiration-2004, 2005, 2009
Sensation -4/2007, 10/2009
2/2010 & 11/3/2011