Gould once said, after a performance, "It wasn't my best. I've only played it 30 times." (I'm paraphrasing here but you get my drift.)
The point is, a piece is never "done". Oh, you can perfect it, but when you come back to it 10, 20 years from now, do you really think you'll play it the same way?
More experience in life and music will change your opinion of how a piece should be played. Vladimir Horowitz probably never, ever played the Chopin Ballade 1 the same way twice throughout his life.
Phil