In Oracle 11g release, schema password is expired periodically, by default this is 180 days. However, if required we can alter this setting and make the password permanent. This change needs to be done to the profile of the schema, all schemas under this profile is affected.
select PROFILE from dba_users where username = ‘User you are interested in’;
ALTER PROFILE <Profile from ABOVE query> PASSWORD_LIFE_TIME UNLIMITED;