jpg files only deteriorate when you save them again, if not "messed with" or just copied they should be fine, the degradation occurs because the jpg file is compressed, so when re-saving an already compressed file, you lose more data each time you save. To edit I would revert to original and save it in tiff or some other raw format until you have a final form you can save again to jpg format, keeping the tiff or raw original for additional edits as needed down the road.