There is no progress without possible failure in medicine.
Each treatment starts with assumptions and you can only go so far until you start testing on actual people.
Until we understand the mechanisms completely there is no way around that.
Genes are an important part of lifeforms. Of course, you may object to tinkering with them and wait until nature has done the tinkering for you. That will inevitably slow down progress by obtaining information so much slower that countless lives will be miserable due to missing cures and treatments.
This is a zone where there is no clear moral answer.
The only thing I would say with confidence is that gene editing is very likely the key to a plethora of treatments and preventative measures.
> Will they need to live their whole life for us to confirm the cure worked?
People already do that right now without gene editing. A friend of mine is 10 years over the life expectancy of their condition just because their parents decided to have them live their whole life "to confirm the treatment worked".
9 out of 10 people with that condition died by the age of 12 if not within the first year of birth.
I'd wager being part of a medical/scientific program to monitor your condition is the least of your concerns at that point.