Hmmm…. Yes, I guess I could now that all the editing is done and I don’t need them floating there in the center of the world.
To make things a bit clearer (hopefully):
A 3D model is just a list of Vertex (and Edge and Face…)information
A linked duplicate is an object with the same information about where it’s Vertices are (in relation to it’s Origin), you can delete any one of those duplicates, or even it’s original, and no information will be lost.
This plank:

has the same Vertex info as this one:
Deleting the original plank, doesn’t delete the list!