Re-using an import removed prior import image files

[MandyDennis]

Q. Can someone advise if it is best to delete Import (flimp) files after used?
Background:
I have been importing Word files in stages for a growing Help project and re-used a prior Import file, only to find many images from the previous import were removed during import of the new content.
I do not link generated files to source files.
In re-using the Import file, I deleted the previous Word file from Source Files and added the new content Word file.
All looked fine until I later discovered 'missing file' messages all through topics.
I take entire project copy before big steps, so was able to roll-back and start with a new Import file.
I now have a growing list of Import files, I will likely not use in the same format again.
But am unsure what went wrong and now wary of the Import files breaking content.
Q. Can I just delete them safely?