Thomas Aquinas

“ Now some diseases do not last long; so that if this sacrament is given at the time that the sick man is in a state of danger of death, he does not leave that state except the disease be cured, and thus he needs not to be anointed again. But if he has a relapse, it will be a second sickness, and he can be anointed again. on the other hand some diseases are of long duration, as hectic fever, dropsy and the like, and those who lie sick of them should not be anointed until they seem to be in danger of death. ”

“ Whether it ought to be repeated during the same sickness?
Art. 1 - Whether this sacrament ought to be repeated? Objection 1: It would seem that this sacrament ought not to be repeated. For the anointing of a man is of greater import than the anointing of a stone. But the anointing of an altar is not repeated, unless the altar be shattered. Neither, therefore, should Extreme Unction, whereby a man is anointed, be repeated. ”