I think its been about 2 years since the last time the snowball launchers appeared. I seem to remember getting them around then. They definitely were not given last year, and the EvE-O forums were very vocal about it.

If the forum post from CCP can be taken literally, I would guess that early January the snowballs will melt. From the post:

"our current estimates is that the effects of said storm will be in effect until downtime January 6, 2009"