How long does a Christmas Tree last?
The standard answer is 4 weeks, and the image shown here is a tree that was cut down at the start of December and picked up after Christmas. The needles are straight, fresh and green.
There are basic guidelines such as cut the base, fresh water, out of the heat, less lights the better but generally they will stay good.
However they are individual plants, with different characteristics, and some are just better than others.