If you are in a situation where you are forced to resort to whacking away at the stone with your knife, I think you have a lot more to worry about than maintaining it's edge. This isn't some kind of lightsaber! It is only a very sturdy, durable, well-made <i>knife</i>! Use it as such... dig with it, chop vegetation with it, cook, clean and dress with it, pry things open with it - and if you've <i>really</i> screwed up, defend yourself with it. And above all... Take care of it!
Care for your gear and it will take care of you. If you're digging out a fighting hole with it and "encounter" some rocks, don't be surprised when you find that afterwards it isn't as pretty and sharp as it was before. If you have to wedge it into a doorjamb and use it as a prybar, you can be confident that it won't bend or snap, but the edge may get dinged as well as the finish. Also, after exposure to salt water, rinse it off and wipe it down with tuff-cloth or a similar product. Keep some in your pack if necessary.
Any well made tool of this nature is designed to be able to stand up to a higher level of abuse and neglect. Lord knows they need to be durable. But this kind of testing strikes me as somewhat asinine. Just because it <i><B>can</B></i> handle the abuse and neglect doesn't mean that you should do that unnecessarily. Please don't take this wrong. I have a tendency for bluntness sometimes. I just see this kind of test and say to myself, "There goes several hundred dollars and hard work... unnecessarily pi$$ed away!"