I am wondering the best way to model a in the context of an assembly, when that same part is movable in that same assembly (such as with a hinge or pivot point).

For example, I am modeling a box that has a hinged lid.  The lid is able to pivot on its hinge.  I want to model the lid so that its dimensions are driven by the other dimensions of the box body when the lid is closed. But, I also want to be able to show the lid in its open position or anywhere in-between.  And the lid's dimensions need to stay the same no matter what position I have it in.

Right now I accomplish this by first modeling the lid in its closed position (with mates that restrict it there), and then I hide the lid and add a second instance of it to the assembly, this time with fewer mates so that it is able to pivot as desired.  This works, but it is cumbersome and also the part would show up in duplicate in the bill of materials. 

Does anybody know if there is a better or proper way to handle this situation?