Not sure I follow you here. VR has no effect on camera exposure, but the shutter speed has an influence on how effective the VR is

VR reduces the lack of sharpness due to camera shake. Without VR camera shake is usually a problem at a shutter speed of 1/the focal length of the lens, and slower. Lets say you have your lens set at 125mm and VR turned off:

- At 1/250s your image should be sharp
- At 1/125s the image will start to be a bit blurred.
- At 1/8s your image will be blurred and unusable

Now turn on the VR

- At 1/250s the image should be sharp
- At 1/125s the image should be sharp
- At 1/8s the image will be starting to be a bit blurred

VR doesn't help you:

- When the shutter speed is fast enough for camera shake not to be a problem anyway
- If the subject is moving
- If you press the shutter release like you were playing the piano in Carnegie Hall