Not true that you can only have it once. You can be anointed more than once.
If you are about to have surgery, for instance, and all surgeries are risky and there may be a chance, however remote, that you might die on the table, you can be anointed for that, even if you pull through.
If, after that, you find yourself in some other life-threatening situation, you are seriously sick again, or are seriously injured, and the outcome is iffy, you can be anointed again.
Anointing of the sick, or of people in other life threatening situations, is a sacrament that is entirely repeatable, because one doesn’t know what the final outcome will be. Not everyone who gets the sacrament dies, but that certainly doesn’t preclude one’s getting it again if there’s a risk again of them dying.
It wouldn’t be right to deny anyone being anointed who is in danger of dying simply because they were in danger once before and needed the sacrament. I know of no priest who would refuse that, even if he knew about the previous incident.