Live trees or aritificial? The package should be timed to arrive as near as possible with your check in. Can't give you a guess on how long, because I don't know where you are shipping them from. If artificial, there shouldn't be much of a problem, they'll just store the package until you check in and ask for it. Live trees could be dodgy. They'll require care, of course and that might not be something the CMs are able (or aware) to do.