Nascence

It's Incendia, isn't it?
I think it never stops and says "finished!" You can stop the render whenever you want.
Sometimes the changes of a longer calculation are minor and you'll only see them, when you zoom in into the saved picture: the surface looks smother and some "dirt pixels" are gone. Sometimes the longer you let the program work, the more intense the fog and glow will grow. So it's your point to find a "good ending".