I've been ruminating on this comment for many of the last 21 hours, in part because I want to give a good answer and in part because I suspect I see the direction of the conversation.

I think the answer is, of course I don't want my kid to die, but I want them to be able to without suffering when and if they're ready to and mature enough to make such a decision.

QoL not declining kind of seems like a fantasy to me. Taken literally, living "forever" means that you'd outlive the planet, the sun, ultimately the universe. Sounds like a lonely and eventually boring life though, yes, you'd likely experience a lot of thrills before that point. IIRC, among other media, there's a section of H2G2 that briefly addresses this.

Taken less literally, there are mornings during which I wake up and think "I have to go through with this for how much longer?" If I could spend the rest of time without physical or mental health once dipping, I might feel differently, but especially the latter seems unlikely to me (even if it is a laudable goal).

For anyone reading this with concern, I'm happy with my life, I'm not depressed and I'm not at risk. If you were going to say something about that, thank you for caring, but it's not necessary.

edit: Added detail.