January 12 is the cut off date. Except in retail, where all the Christmas decorations come down in the evening of Christmas Eve...
I put up our Christmas tree last year and its still up. Its very tiny, about as tall as a shoe, it sits on top of the TV, I thought about putting it all away in April and then September came around and I thought stuff it.. So this year for Christmas I moved to the coffee table and will actually put it away when I come back from QLD on the 13th.
Here its quite common to pack trees up well before NYE. A lot of people like to get a real tree and I think the Aussie climate tends to dry them out really quick after they have been cut, so by the time Christmas comes a lot of peoples trees have started to brown and look unsightly, so a few days after Christmas its quite common to see them dumped by the roadside like someone has disposed of a body...