Ok, maybe you don't have to state the conditions, but you have to predict that there will be an actual time that you want to die.

I don't follow your utility comparison. I don't think of utility as a number in this way, but even if so, that's not the deal being offered.

In order to not want immortality, you have to want to die. I think this is pretty straightforward. The deal being offered is "you expect some utility amount every moment you experience. some of these may be negative. You have some influence, but not actual control, over future experiences" If you predict that the sum of future experiences is negative, you would be better off dieing now. If you predict positive, you should continue living.

Unless you can predict a point at which you want to die, you should predict that you'll want to live.