I draw airplanes with details of parts. EVERYTHING is either a group, if used only once, but always a component if used at least once or twice in the drawing. There are NO "free" entities in a drawing.
Then I organize the collection using LAYERS. I number each layer in a hierarchy, and assign whatever appropriate groups/comps to a layer.
Where I have components that move (ie: landing gear up or landing gear down, I create a layer for each, and a copy of the comp assigned to each. You can orient/move/rotate any comp. and retain its entity integrity. Only if a secondary comp. has a minor entity change would I make it unique. But that dissolves the link back to the original.
One other important detail. Every single entity in the drawing is on LEVEL 0, whether in free space, in a group or in a component. Only groups and components bounding boxes get assigned to a specific layer. It can be layer 0.
That way, you can easily control visibility, create scenes and do other neat stuff.
