What should one who vowed to fast an entire lifetime do, when he is now old and unable to fulfill his vow?

Many scholars have held the view that it is permissible to vow to fast perpetually. If the one who made the vow becomes unable to fulfill it due to old age or a chronic illness from which recovery is not expected, then an expiation for breaking an oath becomes obligatory upon him. There is a difference of opinion as to whether he is also obligated to feed one needy person one mudd (a measure of food) for each day he missed, or if nothing is incumbent upon him except the expiation for breaking an oath. However, if the inability is expected to cease, he should wait, and no expiation is binding upon him.