> Sure, people will kill themselves in difficult situations
> (and/or because their brains are out of balance), but strictly
> speaking this isn't rational, certainly not in this day and age
> with its prospect of immortality and sustainable mood enhancement
> (among other things).
Sustainable mood enhancement? Should my life's goal be a lobotomy and a morphine drip? You seem to be advocating a Mario Brothers vision of meaningful life - stay alive as long as possible so you can keep jumping for pleasure points. Even positing that this is the only rational course, why would suicide not be justified if I have good reason to belive my total score from this point on will be less than zero - as I belive was the motivation for the hypothetical life imprisonment scenario?
And why should the rational course necessarily be determined the simple summation of all future pleasurable experiences? It seems to me there's a factor in the sequence which decays over time - I wouldn't submit to a million years of agony, starting now, even if the following million were quite nice.
Pleasure is a good way to pass the time, but being dead doesn't mean you've lost, it means you've stopped playing the game. Honestly, I can't imagine anything more horrible than the prospect of living literally forever.