Patch Manager security questions

I have a few questions about patch manager in regard to security and security management of the service accounts in the credential ring.

1. Does a password length limitation exist for the credentials within the credential ring?

2. Can the credential password be changed in an automated manner instead of using the credential ring wizard?  The desire would be to change it on a daily or weekly basis without using the interface. 

3. How is the password stored and where within the product (database, config file, etc)

Thanks for the help!