And...I am nearly caught up!
Heck...soemtimes I scrap the same picture on two different pages...sick I know.
To answer your question, however.....I save my duplicates that I don't use. I either use them on pages for family members, or save them for the kids to use.
Someday, you may just need them...think of school events where they ask for pictures. I would keep them in a box in photo safe albums, sorted like I do for scrapping.
Patti