Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
All the Muslim scholars are agreed that Mahr (Bridal money) is a precondition for the validity of the marriage contract. Therefore, making a mutual agreement on leaving it is not permissible. Paying the entire Mahr at the marriage contract is what is required. But it is permissible to delay that Mahr or part of it if there is an agreement between the two parties on that. Hence you may agree to receive the Mahr late and your approval for delaying the Mahr should be either for a given period or for undefined one.
If you agreed to delay receiving the Mahr for a certain period then you have no right to demand it before that period even if your husband divorces you. But in the case of your husband's death or if he becomes bankrupt then right after his death or declaration of bankruptcy you may demand your right.
If there is a declared time for paying the Mahr or there is a tradition known in the community that delayed Mahr is paid only when the husband dies or when he divorces his wife, then he is not obliged to pay the Mahr before the occurrence of one of these conditions.
Allah knows best.