One of the essential conditions for the validity of the option of condition that the condition is to be known and determined so that it is not probable to be high and low. But sometimes this period is mentioned in such a way that observe the above condition is doubtful. The sentence of condition of option for life-long period is accompanied by silence of the law whereas article 401 Civil Law consider specifying time as essential description. In this regard, there is disagreement among lawyers and jurists. The correctness of the condition, assuming the other requirements, provided the validity of the conditional contract and invalidity of condition leads to doubt in validity or voidance of contract. Being aleatory and revocable of conditional contract, of important difficulty of dissent viewpoints which faced with answers and arguments from the condition advocates. In this study through discussion and analyzing available believes and decisions and review of relevant legal material, the validity of this condition is much more preferable against voidance of the condition.