DL changed the terms of the SM program in August of 2009 to allow choice awards.
As of October 1, the skymiles program does not give SWUs but gives you a choice of benefits.
One of them is 20k miles, the other is 4 SWUs the last is the ability to gift Silver.
All of them can be chosen immediately.
AFAIK, the gift of 6 SWUs on attaining Plat was under the terms of the old program which DL changed, with much fanfare, upon introduction of the new program in Aug 2009.
Hope that helps. YMMV. Please respectfully ask Kevin Pinto. and all that disclaimers.
I was hoping this thread was about Shena Nigans as well, but was disappointed to find her older sister Sky Nigans.
Actually, this wasn't done consistently. I was one of the fortunate ones who received 2009 and 2010 benefits, despite changing status near the end of the year. I qualified for Platinum on Dec. 4 and received a 2009 plat packet, including 6 paper SWU certificates, during the first week of January. The SWUs were later converted to electronic certificates. They are valid until the end of Feb. 2011. I also have the choice benefits for 2010, including the option to get four more SWUs.