Day was very difficult when SSO(admin@system-domain) account got expired and I learned that SSO Password expires in 1 Year. Suggest you to create an alternate account and keep reminder.
Best solution which i got was Login to database and go to Database>RSA>Table>dbo.IMS_AUTHN_PASSWORD_POLICY
Right Click on Table>Select Edit Top 200 Rows….
Go to Column _MAX_LIFE_SEC and increase to any suitable value.
Finally got saved !!!