It could happen that the edition of armatars containing your 'green fluffy armatar' will return next year for you to use...
But if you want to make sure that you always keep the one you like best, there's only one thing to do... never change it!
I have the 'Flaming Sun Armatar' from the moment I joined AG back in 2009 and because I like it a lot, I never changed it... and I'm glad I never did, because it hasn't come around this year! *wipes forehead*