Wow; what a gorgeous picture!
I’m not patient enough for diamond art, but my 14-year-old son is very much into it. He has been saving the extra drills (I honestly only now learned they’re called this lol) in case he loses any for future projects, which sometimes happens in a house full of people with ADHD and a cat who likes to knock over things 
The extra drills have come in handy at least once. We accidentally ruined a diamond art canvas, but my good friend said she could salvage it. So we gave the extra drills to her to fill it in, since it was already half full, but salvaging it might ruin some of the already placed drills.
I have wondered about creating my own design and using whatever leftover drills he has if he doesn’t want them anymore, but I have too many projects I want to do more lol
But if you ever decide you don’t want the leftovers anymore, you might find someone to share them with in the sharing and caring “give-along” 