Cory Doctorow's wonderful sci-fi book "Down and Out in the Magic Kingdom" explored exactly this in interesting ways. In the book people in the future can live essentially forever by transferring their consciousness into new bodies. They can also back up the contents of their consciousness, something most people do nightly but certainly before doing some dangerous extreme sport. Doing dangerous things without backing yourself up is considered tantamount to suicide since you lose all the memories and personal growth, essentially the person you became since your last backup.
People do get bored and will sometimes choose to "deadhead" for hundreds of years at a time, which is putting yourself into stasis and skipping those centuries. The book is full of provocative ideas about how practical immortality might actually work on a personal and societal level.
Mind uploading? That’s a whole other level of sci-fi. It isn’t extrapolating what we already have, it is waving your hand and declaring “as far as we know it isn’t physically impossible so why wouldn’t we get there eventually?”
Plus it raises all these difficult questions about the philosophy of mind and theory of personal identity - is the backup actually you? Or do you die, and you are survived by someone else who isn’t you but thinks they are?
You don’t need sci-fi mind backups for that. How certain are you that when you go to sleep tonight, the person who wakes up tomorrow will be „actually you”? How certain are you that all your memories were lived by „actually you”?
The answer, I suppose, is that we don’t know what „actually you” even means, how consciousness works, or why you’ve even got a (seemingly) continuous internal experience.
I view life (in the philosophical sense; consciousness) as the stream of subjective experiences (qualia) that arise out of life (in the biological sense; neurons and such). Right now my life consists of a collection of sustained interest in this discussion, a little hunger, the qualia of seeing the screen and the realization that I'm sitting a bit uncomfortably. In a few moments "I" will be a collection of other ephemeral qualia.
There's no "real" continuation between one experience and then next, just like there's no real continuation between my past "self" and my future "self", but they're both extremely useful illusions. I'll eat to subside that hunger that was registered a moment ago or change my position to get comfortable. I'll be responsible for "my" previous actions, as well. I'll basically be able to function as a temporally continuous being.
On the topic of immortality, I'd like to be virtually immortal so I can pursue my goals indefinitely. If I stop having goals or feel like I've had enough, I could always kill myself. My goals arise from my ethics, my biological needs and probably many other things. Why would I be OK with biology and death preventing me from achieving my goals at some arbitrary age?
So for me "immortality" is both being able to continue the illusions of self indefinitely (which I admit, feels good intrinsically), and being to continue the pursuit of my goals indefinitely. The goals seem to actually have more "real" continuity than "I" do.
The most troubling thing with immortality is the biological imperative to live that makes suicide so hard. But I think after a few centuries many people will reach that point. It's not a bad thing, it's just a personal choice.
We can already change the maximum lifespan of some other species. Why shouldn’t we expect to gradually be able to do it for more species? And then what makes humans special that we couldn’t eventually do the same for humans?
And my point was-no matter how hard human life extension is, mind uploading is many orders of magnitude harder. The first, it seems likely in principle that we could achieve it if only we knew the right genetic changes to make-now, you may be right that in a thousand years we still won’t work out in practice exactly what they are-but human life extension has a certain kind of theoretical in principle feasibility which could well coexist with practical infeasibility; mind uploading lacks even that level of theoretical in principle feasibility.
Death is a certainty. No amount of technology can change that even theoretically. We don't even have reason to be confident that the universe itself is eternal, let alone any component of it.
If that is immortality then we may as well call it a tautology and say we're already immortal. None of the things that make people who they are need to be preserved to achieve it so we're realistically already there.
Living an absurdly long time I can get behind. Billions of years, trillions of years, unimaginable numbers of years, sure. That could happen. But immortality isn't an option, everything eventually dies off unless we play semantic games where there aren't any properties of the thing that need to be preserved. And maybe even reality has an expiration date for all we know, which would render the whole project moot.
For some people, the idea that their present conscious moment might eventually be left permanently without any future extension is terrifying-but provided that doesn’t happen, they might be neutral (or even positive) about the prospect of the contents of that consciousness eventually becoming so radically transformed that it becomes a completely different person, or even something which transcends human notions of personhood, albeit ultimately still continuous with the person they are now. For other people, that prospect is terrifying. It really depends on what one is most attached to - the mere continuation of one’s own consciousness, or its distinctive contents that makes you you.
It might look like immortality to outside observers, but I don't see how it is the same thing
Any process that could theoretically allow me to exist at the same time as my future self must clearly not be me anymore
So any kind if "mind backup" is a copy. A clone with a copy of my memories absolutely cannot be me. We would somehow need to be able to transfer my consciousness into a clone body
It seems very likely to me that consciousness is actually a side effect of a physical network in the brain and cannot actually be separated from the biological brain to move to an artificial brain
I'd be thrilled to have another handful of centuries though. It doesn't have to be forever to be valuable
One character has an entire island of populated exclusively by herself.
They never go into why it’s illegal. I think it’s implied they know a copy isn’t the original, but they don’t want to think about it. Too unpleasant an idea.