Check out my 2007 spontaneous activation post, its my experience on it.
Personally, I don't take spontaneous activation much of a thing, it just like remembering where you put your keys and nothing very special about it.
I doubt people would simply sit and wait for spontaneous activation for any average size books, because even spontaneous activation did happen, it won't get you very far through the book at all.
So, don't stress on it too much.
