I think changing passwords regularly is a good practice. I personally change passwords from important accounts monthly, give or take. So I use a helpful checkbox "Expires" and set an expiration date (current date + one month) manually each time I change a password.
I believe it would be convenient to automate this activity: if an entry's checkbox "Expires" is checked already (the expiration period should be remembered from the last time it was set), changing the password sets expiration date (current date + previously set period) automatically. Or a dialogue prompt should appear asking if a user wants to update the expiration date together with the password. Would be great, I believe.