I'm Italian, so I never take any of our Christmas decorations down until Epiphany, which is January 6th.
We have three trees - two fake, which I put up November 11th this year (usually do it the day after Thanksgiving, but this year I knew I would be travelling and wanted to enjoy them longer), and the live tree went up the first weekend in December. Its already starting to look a little dry, but I keep changing the water and spritzing it, so hopefully it will last until January 6th.