12 years... it's funny, right? It could've been so simple. 14 years ago, a crush, way too high expectations lead to a crash when rejected. A psychologist could've helped. 13 years ago, no sense of self-worth, I find refuge in a MMORPG. A psychologist could've helped. 12 years ago, love at first sight, still utterly broken, frozen with anxiety, can't even say hi, neither in person, nor online. Self-hatred grows day by day. Get a psychiatrist in the mix, and it's probably still fine. Eventually suicide seems like the way out. I set up a date. In the meantime, I figure that if I hate myself so much, I can't escape, I must stay and suffer.
It's absurd what an inexperienced mind can come up if left to its own devices, there was no need for any of this.
Years go by, I actually built up confidence. As I achieve things that kid would never think possible, it's evident he was very wrong. Yet, satisfaction is lacking, something is broken beyond repair and it's not worth trying, unless... alcohol and illegal drugs! But not really, the drugs don't work.
You know what could work, if anything? Proper professional help. And you know why it's hard to admit? Because I'd have to recognize that it really could have happened much sooner and I let an ignorant scared 13 y.o. control my life for so long. I should probably try it, don't know if I will, and you should too.
Your therapist knows that most people can be helped, despite feeling otherwise, and they know some are beyond help. I don't think pro-lifers are correct when they say suicide just transfers the pain to somebody else, because what irradiates is always more manageable than what the suicidal person went through. Otherwise, humanity would have extinct already. But I do believe the odds of recovering are very good, and the way to end with the lesser amount of suffering in the world is to promote recovery, but allow a peaceful exit for the ones who can't do it. This is all in theory of course, practice is much harder.
EDIT: sorry, I forgot to actually answer your question. How long? I don't know. Ideally, you'd just be open about your feelings and make it clear whether it's working or not. I don't think the family would ever be completely ready for it, but any effort in this sense should make grieving easier to handle, if only a tiny bit.