It would be good customer service to give some fore warning to the patron that their password is going to expire soon, just like we do with account expirations. It would also be good to remind them when the password has expired.
This is particularly important with STAFF accounts that are SHARED. It is common practice around here for libraries to have a shared circulation account so the library is managing less accounts. However, it would be best if a notification is sent out, so that someone doesn't change it on the fly and forget to tell everyone else.