I will give you a very concrete example.
In 25 years of psychiatry and 30 years in a hospital setting, I've seen two cases where patients could have requested MAiD and might have succeeded in getting it. Given the current guidelines, it's impossible to get it at age 20 or 25. Moreover, a patient cannot get it during an untreated episode of major depression or if they don't have a long history of pain and suffering.
If a patient has been suffering for 10 or 15 years despite treatments that an independent expert considers to be relatively optimal, and if therapeutic trials are conducted and, for any number of reasons, a dark cloud still hangs over the patient's head, MAiD might be an option.
It's important to understand that some people have lived extremely hard lives and it can be extremely complex to treat certain health issues. If I say to you that someone has cancer of the soul and and it's untreatable, would you say we should condemn them to a life of suffering? Should they be deprived of that freedom to choose?
I would tend to say you have to take into account the desire for death in someone who is not capable of living and has tried everything. We're not talking about someone who's been abandoned by the health care system. We can look at the nature of the treatment, the longevity of the treatment, the intensity of the suffering and, most importantly, the duration of the suffering, including all the health conditions the patient suffers from.
You also need to consider agreement from the person and their entourage, their family, who have watched them live for 10, 15 or 20 years. In that context, do you truly risk being wrong about the prognosis? I don't think so.