The Coins that you earn on Club Nintendo are good for two calendar years, so as it's March 2012 at the time of this writing, those Coins that you've earned already can be used or held on to until March 2014. Your Elite Status gets reset at the end of a Club Nintendo year, not the Coins that you have. As for the matter of your other Coins, it depends. Since Nintendo removed the option to see what year a survey expires, you may want fill those out to earn those Coins just so you won't lose them. For the Coins that you can earn using by the remaining PIN codes that you own (and completing those Post-Play surveys after entering the PIN code), it might be better to wait on using those. The Club Nintendo year ends on June 30, so by saving the PIN codes you haven't used yet, you can get a jump-start on the new Club Nintendo year when it starts on July 1. Remember, you only need 600 Coins in order to reach the Platinum status.

Oh, and as for your question about Coins "rolling over" towards the Elite status of a new Club Nintendo year, the answer is they will not. You'll still be able to have your Coins for two years, but anything over 600 Coins that you earn in a Club Nintendo year will just be extra. If you want to earn the Platinum status reward every year, you'll need to earn another 600 Coins.

I don't want to brag, but I'm at gold for 2013 already, and was platinum in 2009, 2010, 2011 and 2012. I'll be platinum again in 2013 after I get the 3DSXL (I'm only 160 away now). How did I get platinum every year? Well, it goes back to the original my.nintendo account. I had over 100 games registered. Since I had so freakishly many, I did all those surveys, stopping after I reached 600 coins the first Club Nintendo year. I saved the games I didn't register and surveys since they didn't expire until years later. I also bought games during the year, but didn't register them since I was already platinum. I registered them the following year, again stopping at roughly 600. I then did 60 surveys that got me platinum in 2011. Since I had no games registered, I did them last year getting me platinum again in 2012.

What got me to gold this time was the 3DS, a few games I wanted on the shop, but didn't buy until a couple months before this new year started. I did all my surveys since they expire in just 120 days. Point is, when you buy the game, if you have already reached platinum, do NOT register it until July 1 or later!! Plus, keep looking at the intend to buy surveys, sure you'll lose the 10 bonus coins for registering within a month, but you'll gain 10 with the intend to buy which lasts YEARS! I say if you got the status you want, STOP, do NOT register anymore!! If you really want a prize, be patient, if you register all the stuff you saved on July 1, the reward will most likely still be there. If not, it will be popular enough for Nintnedo to bring it back (like the Mario Posters right now).

Some argue you'll miss rewards, but think about it, the highest are 800 and 1200, by the time you get 1200, it will STILL be available, as it take a LOT to reach those many to begin with. Most can be bought during the 600. Yes, some are gone now, so you'll have to go via the online route, but you can at least get them new that way.