I just got my copy of "Forskaen Lore" today. I was flipping through all of the the additional copies of the existing spells when I had and interesting thought (at least I found it interesting).
I ran a session of Mansions of Madness for a group of friends last week and I like how the spells cards in Mansions, on a successful casting, usually instruct the player to "Discard this card and draw another copy of [Insert Spell Name]". It occured to me that you could easily add that mechanic to the spells in Eldrich Horror.
Why? Because magic is always in flux. The same number of successes that let you raise two different skills with "Feed Your Mind" today might overload your mind and cause you take sanity damage tomorrow and might draw the wrong kind of attention and earn you a Dark Pact the next day.