All* joking aside, WPA2 is strong enough to require supercomputers running parallel-computing over many days in order to break it (and they still haven't). I would suggest the hum of a few Crays sat on your drive wardriving your wifi might be a little bit of a giveaway. The danger of a long password is more likely that you write it down rather than remember it, which is far more of a concern (especially if you are only protecting a home broadband connection anyway).
(* most)