Rendering separately light sources with render elements (AOVs), then re-assemble them during compositing allow infinite artistic changes without extra rendering, particularly when rendering in 32-bits. Raw compositing allow even more massive lighting changes.
Note: since V-RayNext, light selections must be revisited, check my other tutorials.
Tutorial to watch next: “vr_compositing_pt4” and “vr_light_selection and its compositing in depth”