How long can a cut Christmas tree remain in the house?

FAQ
Question: 

How long can a cut Christmas tree remain in the house?

Answer: 

The length of time a cut Christmas tree can remain in the home is determined by the tree species, the freshness of the tree at purchase, and its placement and care in the home. In general, a fresh, well-cared-for Christmas tree should be able to remain in the home for three to four weeks. Remove the tree from the house when its needles become dry and brittle.