Answer:
Honestly I don't know.
Step-by-step explanation:
I will tell you my thoughts though. I think that artist ask the question "Am I done" because sometimes it helps to be able to feel faithful in your own work. I don't know though. I think that the issues a lot of artist face if they overwork an artwork is always selling out. I think of selling out as not having anymore artistic to expose the piece of art work.
Sorry if I make no since, but like I said "I don't know"
Hope this helps a little bit at least even if it's only like a 5%. "Laugh out loud."