I have also done RtK (book one). It took about 4-6 months over the course of two years (I lost my way a bit in the middle). Anki says I have done 34,000 reviews over 174 hours.

I agree that eventually the stories should be forgotten, but initially, they are significantly better than my normal memory.

In fact I am starting to forget the stories of the kanji that I am exposed to regularly. However, some of the general use characters appear pretty infrequently, and for those the stories are still invaluable. I like Greg's training wheels analogy below.

Another advantage is that the stories provide a check for characters I also know visually. So if I'm writing a character from my visual memory I might be reasonably confident that I'm writing it correctly, but if I can also remember the story then I am sure.

Of course doing RtK doesn't teach you any Japanese, but since I did it I find Japanese vocab acquisition much easier. Maybe it's like learning English when you already know Greek and Latin.