In the Doctor Strange movie, we learn towards the end of the movie that
the Ancient One used the spell described on the page that Kaecilius stole to obtain eternal life.
However, after that reveal, it seems to be completely forgotten. In particular, we don't know
why she even used it (I guess eternal life is motivation enough, but wise people would be more cautious), why she changed her mind about using that spell after that, or why she even could attain eternal life while despising the “big baddy” of the movie, when Mikkelsen's character didn't.
Therefore: what is the point of that reveal? It seems completely unconsenquential for the story told. Did I miss something?