Having the Card itself is very helpful when dealing with lounge staff from other SkyTeam airlines (as a CO Plat card will get you into a SkyTeam Carrier Lounge when you're on an international itinerary on SkyTeam Metal). I once had to place a $1.50/min call on an international cell phone to get the OnePass Elite Desk on the phone to confirm that I was indeed a Plat in good standing so I could enter the ServisAir Lounge in Edinburgh (Back when Plats had lounge access in EDI...prior to the BMI Lounge switch). As my mailing address was in Edinburgh at the time, my Renewed Plat card did not reach me until late march, a good while after the expiry of the old card.

[EDIT] Looks like cpx beat me to the punch by a min or two