Set the password life time to unlimited for DEFAULT profile.
SQL> SELECT resource_name,limit FROM dba_profiles WHERE profile=’DEFAULT’;

RESOURCE_NAME LIMIT
——————————– —————————–
COMPOSITE_LIMIT UNLIMITED
SESSIONS_PER_USER UNLIMITED
CPU_PER_SESSION UNLIMITED
CPU_PER_CALL UNLIMITED
LOGICAL_READS_PER_SESSION UNLIMITED
LOGICAL_READS_PER_CALL UNLIMITED
IDLE_TIME UNLIMITED
CONNECT_TIME UNLIMITED
PRIVATE_SGA UNLIMITED
FAILED_LOGIN_ATTEMPTS 10
PASSWORD_LIFE_TIME 180

RESOURCE_NAME LIMIT
——————————– —————————–
PASSWORD_REUSE_TIME UNLIMITED
PASSWORD_REUSE_MAX UNLIMITED
PASSWORD_VERIFY_FUNCTION NULL
PASSWORD_LOCK_TIME 1
PASSWORD_GRACE_TIME 7

SQL> ALTER PROFILE DEFAULT LIMIT PASSWORD_LIFE_TIME UNLIMITED;