I got a TrueCrypt container which is using a 64 character password. This password contains all the different kind of characters available to me (upper case, lower case, digits, special). It's taken me a long while to remember this password, so I would not want to change it to a completely new password.
What I am protecting is nothing too important, at least for any agency such as NSA. It contains my own private information that I don't want anyone to read. I am more worried about family/friends getting into this container as well as identity thefts.
Now it's time to change password. I been thinking about changing a few characters in this password. I wonder, what's the minimum amount of characters I should change to make it secure enough? Changing it to a completely new password is not an option for me.