The employment of the broker is not usually for a definite time. It is revokable at will in good faith by either party, or by mutual consent. If a reasonable period of time has elapsed and the object has not been performed the agency may be considered at an end. It is also terminated by the death or insanity of either party, by bankruptcy and by the destruction of the subject matter. If the transaction sought has been accomplished, either by the broker himself or by another broker, or by the principal, the employment has ceased.