DavidM,
To answer your initial question, I now think that the more diversified you are with ANYTHING, be it inbound links, anchor texts, or even things like the stock market or your other investments, the better off you will be.
So if you are trying to just be more "stable" , then perhaps getting even some low PR inbound links as opposed to just high ones could be more stable.
Then again, with search engines, there is no such thing as 100% stability. Good luck
