Lightroom :: 4 - Preserve Raw Files After Editing In PS?

I have been using LR4, and am starting to learn Photoshop CS6. I thought I understood that there was not need to make a copy when editing a photo from Lightroom in Photoshop. However, Martin Evening's Lightroom 4 book (page 394 if you have it) states 'once you have converted a photo to black and white in Lightroom and edited in Photoshop, there is no opportunity to go back to the colour original'. He then talked about it being better to create an edit copy version

the original file would be lost in Lightroom. He also suggested that Virtual Copies may not be a good idea - something about if the catalog became corrupted you could lose the Virtual Copies, and it would be better to create a 'Real File'
 
So if I were to do some edits in LR4, including convert to B&W, then do further work in Photoshop, would it be better, or necessary to create another Edit Copy of the file so I had the original + another original I could then do the work on. And shoulkd I do this on all files