A piece of art is truly finished only when is forgotten. Its development otherwise continues in the minds of the observers. Art is either in development or it doesn't exist. If it exists, then it's constantly being developed in our mind and collective subconscious. It's continuously changing and being reinvented, acquiring new meanings and perspectives that depend on the time, the context, and the sensibility of the people carrying on the process.
Art is the representation of an idea that is left to the viewers to explore. It's the suggestion of a thought. A muse of concepts. A seed. It's a forge manufacturing a stream of consciousness and inevitable artistic development that materializes in the lives of the viewers.
As you are creating art what you are doing is planting the seed and starting a process that will finish only when your work will be forgotten. And when you look at a painting or drawing or sculpture, you continue the development of the piece. You become the artist, and you carry forward the torch of artistic expression.
This fundamental nature makes art a process without end goal which value is in its constant development.