Objection 1. It would seem that when a man has recovered charity his previous satisfaction begins to avail, because a gloss on Leviticus 25:25, "If thy brother being impoverished," etc., says that "the fruit of a man's good works should be counted from the time when he sinned." But they would not be counted, unless they derived some efficacy from his subsequent charity. Therefore they begin to avail after he recovers charity.
Objection 2. Further, as the efficacy of satisfaction is hindered by sin, so the efficacy of Baptism is hindered by insincerity. Now Baptism begins to avail when insincerity ceases. Therefore satisfaction begins to avail when sin is taken away.
Objection 3. Further, if a man is given as a penance for the sins he has committed, to fast for several days, and then, after falling again into sin, he completes his penance, he is not told, when he goes to confession a second time, to fast once again. But he would be told to do so, if he did not fulfill his duty of satisfaction by them. Therefore his previous works become valid unto satisfaction, through his subsequent repentance.
On the contrary, Works done without charity were not satisfactory, through being dead works. But they are not quickened by penance. Therefore they do not begin to be satisfactory.
Further, charity does not quicken a work, unless in some way that work proceeds therefrom. But works cannot be acceptable to God, and therefore cannot be satisfactory, unless they be quickened by charity. Since then the works done without charity, in no way proceeded from charity, nor ever can proceed therefrom, they can by no means count towards satisfaction.
I answer that, Some have said that works done while in a state of charity, which are called living works, are meritorious in respect of eternal life, and satisfactory in respect of paying off the debt of punishment; and that by subsequent charity, works done without charity are quickened so as to be satisfactory, but not so as to be meritorious of eternal life. But this is impossible, because works done in charity produce both these effects for the same reason, viz. because they are pleasing to God: wherefore just as charity by its advent cannot make works done without charity to be pleasing in one respect, so neither can it make them pleasing in the other respect.
Reply to Objection 1. This means that the fruits are reckoned, not from the time when he was first in sin, but from the time when he ceased to sin, when, to wit, he was last in sin; unless he was contrite as soon as he had sinned, and did many good actions before he confessed. Or we may say that the greater the contrition the more it alleviates the punishment, and the more good actions a man does while in sin, the more he disposes himself to the grace of contrition, so that it is probable that he owes a smaller debt of punishment. For this reason the priest should use discretion in taking them into account, so as to give him a lighter penance, according as he finds him better disposed.
Reply to Objection 2. Baptism imprints a character on the soul, whereas satisfaction does not. Hence on the advent of charity, which removes both insincerity and sin, it causes Baptism to have its effect, whereas it does not do this for satisfaction. Moreover Baptism confers justification in virtue of the deed [ex opere operato] which is not man's deed but God's, wherefore it does not become a lifeless deed as satisfaction does, which is a deed of man.
Reply to Objection 3. Sometimes satisfaction is such as to leave an effect in the person who makes satisfaction, even after the act of satisfaction has been done; thus fasting leaves the body weak, and almsdeeds result in a diminution of a person's substance, and so on. In such cases there is no need to repeat the works of satisfaction if they have been done while in a state of sin, because through penance they are acceptable to God in the result they leave behind. But when a work of satisfaction leaves behind no effect in the person that does satisfaction, it needs to be repeated, as in the case of prayer and so forth. Interior works, since they pass away altogether, are nowise quickened, and must be repeated.
Source: Summa Theologica (New Advent)