Richard Feynman was fond of giving the following advice on how to be a genius. You have to keep a dozen of your favorite problems constantly present in your mind, although by and large they will lay in a dormant state. Every time you hear or read a new trick or a new result, test it against each of your twelve problems to see whether it helps. Every once in a while there will be a hit, and people will say: "How did he do it? He must be a genius!"
Without sounding too self-congratulatory, that sounds a whole lot like the "rehearsal" stage I go through when planning a project. When something is still unformed, it sits on a mental shelf along with a great many other projects, and then as I bump into things in my daily life, I take it down and hold it up to the light of whatever it is I'm standing in front of, and ask myself "Good fit?"
It might take a long time for something to click, but once it clicks, it clicks all the way in. No good story ever takes too long to write.