Oracle passwords - how do you handle this?

At our site, we have about 12 different instances of Oracle (with more on the way). One thing that is becomming more of a problem is the number of separate Oracle accounts that some users need, and maintaining the passwords for these accounts. Since Oracle itsself doesn't have any method of password expiration, some of our inhouse applications now implement a method of doing this, and forcing the user to reset their password after x number of days. The problem here is that if someone changes their password as required by application A, they don't really know that this is the same account/password for applications C and D, but that applications E and F still use thier old password because it's in a different instance.

My question is: How do others handle this? Is there some (fairly easy) way to propogate a password change to other instances where the use has an account? Do you just avoid using personal accounts for Oracle applications?