B.C.
Before we had our son, we use to put the tree up and decorate it on Christmas Eve, then leave it up for two weeks. Now we put it up two weeks before Christmas and take it down first weekend after Three Kings Day (Jan 6th). We enjoy the look and smell of the Frasier fir we get and we think that is about as long as we want to go before it dries out too much and starts dropping needles like crazy. In some countries (Spain I think), Three Kings Day is the day people exchange gifts instead of Christmas day.