Don't trust all your bacon to long password with dictionary words alone. These very long and hard passwords were cracked [thereisnofatebutwhatwemake] and [Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn1]
Here's the article about it on Ars Turbo-charged cracking comes to long passwords.
Essentially, if a hacker can obtain the encrypted password list by hacking into the login server then there is a good chance most username and password will be cracked within a couple days.
I think most password got stolen from the client side with a key logger or something similar. So long and hard password is probably only useful when SE fails and got hacked. By then you'll probably get asked to change your password anyways. As long as your password is not password1 or something similar then it should be ok.