login - When should the message informing the user that the password they entered is wrong go away?

This is a follow up to this question since it got closed. In a log in form, after the user enters the wrong password, when should the message saying "wrong password or user name" go away? For example should it go away after the first character of the password is typed? This is assuming the message is in plain text beneath the password field (not an alert window or anything like that).