From my understanding, the length of the password is crucial, when talking crack/brute force time.
Example :
"The dog took me for a walk two times today. But I couldn't see the bird behind the tree"
That is a fairly strong password. However you might want to look at using random characters for generating the password if you want to make it more secure (but that might be too excessive for what is needed).
-Danny explains this much better above.