1) Freezing is NOT a humane method of euthanasia. So we don't put anybody in the freezer.
2)RI is a pretty broad term, so it isn't accurate to just make a blanket statement that RIs can never be cured. Did you have a culture done to find out what you are dealing with? When someone says a snake has a RI, they are talking about symptoms, unless a culture has already been done. And there are lots of things that can cause a snake to show respiratory symptoms. It could be bacterial, viral, fungal, or environmental. Even if it's bacterial, if the bacteria isn't sensitive to the antibiotic you are using, you are wasting your time.