This may already exist... but if it does, I haven't been able to find it.
We have a password state install that has been running for a few years, and it was started from a password list in Excel that was several years old. We have a lot of old, invalid accounts in our database that don't get cleaned up.
What I would find useful, would be a way to filter passwords (perhaps an automatically populated "password list") that showed passwords that have not been used in the last x days, weeks or months. I expect you already keep the auditing data to make this possible... it would just require some fancy querying.
It would also be good to be able to search based on when the password was added to the database.