Everybody is different in their beliefs, but traditionally Christmas decorations should come down on January 7, which is the day after Epiphany. In the Catholic tradition, decorations do not go up until closer to Christmas, and they remain up for the full 12 days of Christmas.
Consumerism and holiday eagerness play a role in the decision to put decorations up right after Thanksgiving, which means some people are ready to take them down the day after Christmas. The 12 days of Christmas begin on Christmas day and end on January 5. The next day is Epiphany Day, which is the day that the Three Wise Men came to pay homage to the baby Jesus. However, religious traditions aside, personal preference often decides when individuals choose to take down their decorations.