Thanks for the interesting alternative procedure. I think that using layers for each of some 30 objects would be about equivalent to using a single image with 30 objects. In both procedures, an object is selected, copied, pasted as a layer on a page, moved around and flattened. In the "multi layer image" case an object layer is selected to be copied while in the "multi object single image" case an object is selected to be copied.
I guess that if it's done frequently one could start out with the "multi object single image" and after selecting, copying and placing the object on page A you could also place the object as a layer on page B and not flattened and keep using page B for all objects copied . Page B saved in PSP format then becomes the "multi layer image".
(I do too much thinking!!)