I once had a art professor comment to me that most artists (student artists in this particular case) give up on an idea too quickly. I think that is some truth in that. While there are certainly many who take a particular idea and beat it to death with infinitesimal variations, (and many dealers who encourage it) there is a lot to be said for approaching the same topic or image multiple times, either together or spread out over time.
The question is, have you said everything you have to say? Or perhaps, have you observed everything there is to observe. If you are pushing yourself at all as an artist, your work will evolve naturally. Your techniques will change, your color palate and sensibilities will become more refined, or, at least, change.
Whenever I think about this subject, I think of Claude Monet. There were cathedrals, haystacks and, of course, water lilies. He painted them over, and over, and over. Yet I don’t think that he was simply grinding out something he knew would sell. Each of those paintings was the result of a keen observation. He was chasing an elusive representation of what his eyes saw, and what his hand could capture.
Some may feel that Monet’s work was more decorative than deep (I don’t happen to agree) but there are many other examples where the same images or ideas come up over and over. Jim Dine’s Hearts and Bathrobes, David Smith’s Stainless Steel cubes, Mark Rothko’s shimmering rectangles of color… each were working with an idea that they felt compelled to return to.
I recently came back to an image that I have worked before. In 2006 I produced a 3 plate woodcut of a decommissioned sugar factory that is near my studio. The shape of the structures, the textures of the metal and the play of light all caught my interest. My first version of this differed from much of my work at the time, since I did not push to a full range of values.

2006
Color Woodcut
13 1/4″ x 9 7/8″
Copyright 2006, Dean Russell Thompson

2006
Color Woodcut
13 1/2″ x 9 7/8″
Copyright 2006, Dean Russell Thompson
Do I dislike the originals? No, and it is clear to me from peoples reactions to them that there is something about them that captures the eye. But for me it was time to think it through anew. Something tells me that I am not done yet.