When a re-light is the right choice
Choose a re-light when the view is finished and correct, and you want it at another time of day. The usual cases are a living room for morning and evening, a bedroom at night, a lobby with its feature lighting on, and a 3D elevation night view to go with the daytime one.
It is also the right choice when the original 3D file is no longer available, or when the render came from someone else. We work from the finished image, so the 3D file is not required.

