There's an old quip that the greatest correlation for a country to have supercentenarians is them not issuing proper documentation at birth 120 years ago. So yeah, currently there's a hard limit - around 100, more or less, but with life seldom being worth living after 90. I really wish we'd start investing in breaking this. I'll happen at some point, the only question is when, and I'd think it's obvious why we'd want…
What does that end up looking like though, Logans Run? :D
I can't see a voluntary version of it working because of the very psychological issue you mention, we are inherently self preserving creatures in all but the most unbearable conditions. The other thing with these very personal choices, is that you just don't know until you get there - how do you or I really know if life is not worth living after 90, personally? we haven't experienced it.
I remember my Grandfather, when he was younger, specifically saying he'd rather die than live with a certain disease he saw some other people getting - which wouldn't seem like an unreasonable opinion to most people. Yet after gradually developing the very same disease later in life he certainly was not of the same opinion while he was still lucid... That stuck with me, it's easy to speculate about things you haven't personally experienced, and easy to be wrong about your own state of mind in that situation.