My answer will probably be unsatisfying to you: it's needed when you have enough confidence that all your other options are worse. That depends highly on individual circumstances and values, and not much more can be said in general.

But how can you ever have the confidence that your other options will continue to be worse over a longer time frame?

Almost by definition, if you are in the state of mind to consider suicide, you are probably not accurately and impartially weighing the question proposed — and that means it’s likely mostly independent of individual circumstances and values.

(This is different to how I felt when I was younger, and coming from someone who has had several people close to me feel that way at one point in their lives, and now living incredibly positive lives a few years after the fact)

I can see some limited circumstances where it is carefully and openly considered over a longer period of time — like a terminal illness, or unbearable and unsolvable chronic pain — but those cases are the minority by far.

> Almost by definition, if you are in the state of mind to consider suicide, you are probably not accurately and impartially weighing the question proposed

I just don't believe that. How did you arrive at that conclusion?