Some paintings have the over-finished look. One places certain information on paper, be it shadows, form, or color. After one places the information with which he has a good understanding of, he can choose to stop. If he doesn't stop and then fills the blanks with other things, then he risks doing an overfinished piece.
How "finished" a piece is can roughly be defined by how much information it contains. Thus we can almost say that in order to produce more finished pieces, one needs to expand his knowledge of information. If he goes beyond his ability of grasping certain information, and "invents" information to add to the piece, then the result can be called "over-finished."