I have left UIC and I don't want to change my password. Can I just let it expire?

Explains what happens if a password isn't changed

When you leave UIC, your accounts are flagged to be deleted after a specified grace period, about which you should have received an email notification.  Account deletion notices and password expiration notices are managed separately as the events are not intrinsically related.   If you have received notifications about both, you will lose account access by whichever happens first.  If your password expires before your accounts are deleted and you need to continue accessing your accounts until the end of the grace period, you will need to reset your password.