Gene51 wrote:
You don't "save" anything in Lightroom when editing a raw file. The changes, including the generating of a virtual copy, is stored in the metadata. I often do this when I am looking at whether an image looks better in black and white or color or with split toning. A virtual copy is not an extra photo, and it really doesn't use any more disk space.
Also, note that you can stack your virtual copies with the originals, so you aren't slowed down when browsing through your catalog.