I have always thought that the idea of never dying was horrible. I'm 70; and am planning on living another 15 years (based on parental longevity and current state of health) but were I to find out that I was going to be dead in 6 months, that would be mostly an inconvenience, not a tragedy. It would be inconvenient because I would have to wrap up all the details quickly, and I hate detail work.

I'm not in any hurry to die, but by 70 the juiciest part of life is pretty much over. On the other hand, I finally have some intellectual depth (IMHO) and a perspective that took a long time to achieve. My brain feels like it is working better now than it has in a long time, for some odd reason -- possibly an early sign of on-coming dementia.

People who only live to be 100 have outlived most of the people that were ever important to them -- friends, lovers, spouses, siblings, parents, children, even grandchildren. If one lived forever in perfect, vigorous health and sound mind, one would never be young again, and putting up with people who are more and more unlike yourself might be quite difficult. One would live to see all the horrors of our species decline, and certainly lots of other species' demises. At the end of our species, the person living forever would be alone.

Yes.

So I can date all of those women, visit all of those places, listen to (and write) all of that music, read (and write) all of those books, see all of those sporting events, etc.

You're still young :)

As I am now? No. Something like the Christian afterlife attracts me, though, wherein one's current existence is transformed and elevated to a higher one.

Why do we see it so scary and terrifying though? — Benjamin Dovano

Because it kills us ;) Far more scary and terrifying is the idea of birth.

I'd much rather love as nothing for infinitude.

Is it death (no longer being) or dying (the process of deterioration to the point of no longer being able to sustain life) that they are afraid of (given that for many people the latter is sufficient motivation to hasten the former)?

Death is just the lost of attachments in life ( all material and personal attachments ). if you can do that while living then you are free...

I would say probably a little bit of both