Without knowing any specifics about the destination of the images (print, art gallery, billboard, etc), I can only make general statements:
For personal projects, editing ends whenever you're happy with it.
For paid work, editing ends when the image meets your client's needs.
Ricky, thanks. Each client posts guidelines for submission. Just follow the Yellow Brick Road!
Guidelines for submission don't define when editing is complete or appropriate. They just define mechanics, like what is allowed and not allowed, such as cloning, or " hand of man" content in nature photos. Also the size and color space of submitted images.
As Ricky said, the process is finished when the end user, you or a client, are satisfied.
What you perceive will never quite match the camera's capture, and possibly even after PP.
•Our brains isolate, the camera does not
•Our eyes scan continuously, a camera does not
•We correct distortion the camera does not
•We correct colour shift, the camera does not
•Our brain and eyes adapt to massive tonal differences, the camera less so
•We see in 3D, the camera captures in 2D: we need to create the illusion of depth
•The camera captures a slice of time: we remember time as a distorted continuum
•The camera has no emotional attachment: we do
•Our perception is mediated by gender, age,and culture: the camera is not
The point of all this is that what your brain creates as an image is never what the camera captures. As far as PP goes, I personally feel that less is more... I am not a fan of over managed images: to me they my be 'artistic' but so far from my perception of reality that they look very false.
But, that is the nature of the artistic nature of photography.
Again the almost 100% correct answer was, "For paid work, editing ends when the image meets your client's needs."
Caveat, never show any photo. to anybody, that you are not fully good and happy with. No matter what the client wants. This then falls back to the original answer, "editing ends whenever you're happy with it."