(C) He or she is an insured under a separate automobile liability insurance policy issued to him or her as a named insured, which policy does not provide a defense to the named insured.
An agreement made by the insurer and any named insured more than 60 days following the inception of the policy excluding a designated person by name shall be effective from the date of the agreement and shall, with the signature of a named insured, be conclusive evidence of the validity of the agreement.
That agreement shall remain in force as long as the policy remains in force, and shall apply to any continuation, renewal, or replacement of the policy by the named insured, or reinstatement of the policy within 30 days of any lapse thereof.