Living forever is plausible, but not through any sort of god or magic. With the advancements in medical and other types of technology, it’s possible that in the far future, we’d be able to live longer than the lifespans of the present.
But how long should humanity live anyway? Should we really develop technology to eliminate death and aging? Do we even deserve such a “reward” for our technological innovation?
“Should we” questions are not scientific questions but rather philosophical ones.
Personally I don’t think we are mentally evolved for biological immortality. Some of us could probably adapt to it with varying degrees of success. My personal intuition is that most of us would loose interest after a couple hundred years and voluntarily opt out of having further experiences. Not from unhappiness, more like ennui and lack of novelty. We seem to need a certain amount of emotional stimulation and when you get to a place where there’s truly “nothing new under the sun” then it’s harder to find purpose and meaning. People who could take the (very) long view might stick around just to see what happens to humanity, provided they’re situated so as not to have to struggle to sustain themselves.
Even being naive enough to still be chasing illusions serves as a motivator, and as you age, that sort of thing falls by the wayside.
I have said elsewhere that we are story-telling apes, and stories need ends as well as beginnings and middles. It is the only sort of closure one actually ever gets.
Well, that distills it down pretty well…
Physically, medicine can animate life past a normally expected life span. If you had the burning desire to finish your days as something akin to a potted hydrangea this would be desirable.
Curious as to what living past a normal life expectancy looks like? Visit any nursing home.
Medicine is getting better counteracting the cellular damage that come with advancing age. Where they are less effective is in our wrinkled little brains.
When my mother was dying from dementia I remember reading up on the condition. One statistic still sticks with me. The risk of developing Alzheimers or dementia double every 5 years after a human reaches 65. The other statistic was that having a parent with this condition could potentially double or triple your chances of developing the disease…but that’s not pertinent here…
The neurological conditions are tied to advanced aging. They are always fatal…unless there is a machine taking over for the autonomic duties. Even that has a point where the patient resembles a scene from the Matrix…
Life expectancy in prehistoric times was around 30 years. Today, it’s around 73 globally. Your mileage may vary on where you live and your access to healthcare. While there is no physical record left from a damaged brain in bones, fossils or prehistoric remains discovered, I don’t think I’m out on a thin limb suggesting the prevalence of these conditions in modern humans is related to more than doubling the original design life of the machine…
As mordant suggested, stories require an end. It has been suggested here multiple times that blind faith or dogmatism potentially leads to unfavorable conclusions or outcomes. IMHO, Clinical science put into practice without regard for cause and effect, or “just because we can” is too similar for my tastes.
How long should we live? That is a pretty deep philosophical hole to peer into…
Do we deserve to live forever? Deserve? I so dislike that word. I think people neither deserve living nor its opposite.
How long should humanity live? As a whole? I don’t think there’s a should about it. Perhaps our species of human won’t be as successful as previous species have been. It’s looking rather dim for Homo sapiens. 
Should an individual be able to live longer than the current average? I suppose if they want to. Personally, given the current and inexorable decline in my health, (although I’m not ready to throw in the towel quite yet) I certainly don’t think I’ll want to far exceed today’s average.
That’s only if you view the entire population. If you exclude the high rate of infant and childhood mortality, life expectancy (if one made it into adulthood) was substantially longer. Overall life expectancy for populations today appears much longer because of the dramatic reduction in infant and childhood mortality rates.
Unfortunately, that will start to go down as more people eschew vaccinations.
edited to add: gun violence is also making an increasing impact.
Biological immortality assumes that aging and disease will be at least arrested, if not reversed. So assume that if you were offered biological immortality in your prime – at, say, 35 or 40 years old – you would stay virile, energetic, and healthy (and, presumably, horny, which might or might not be a good thing depending on your point of view; honestly I kind of like not being thusly burdened but YMMV).
But yes if we were just talking about being eternally rickety, there definitely needs to be an end point to THAT, and sooner rather than later.
There’s another angle to this – apart from whether we “should” live long or eternal lives or whether we’d like it as much as we tend to think we might, and that is the question of resource usage.
If biological immortality was not just offered to the elites but was available / affordable to all (unlikely, lol), it doesn’t necessarily follow that everyone would reproduce like rabbits and the earth would choke on trillions of people. Presumably people would not feel the pressure (their clock would not be “ticking”) to have kids before they’re “too old” so that can could be kicked down the road pretty much forever without consequence. Nor would they be reaching for some specific experience that might motivate them to have, say, 3 or 4 kids instead of 1 or 2. It would also become more acceptable to regulate how many children you can have, how often, and under what circumstances – again because you have infinite time in which to have them down the road.
I think that population self-regulates around factors like this and available resources (you can’t have big families when there’s insufficient food, go ahead and try, they will just starve) so I don’t see biological immortality as necessarily a huge problem with resource usage as other factors will regulate the matter.
Of course if there’s no particular hurry to have kids there’s no particular hurry to grow up, choose a profession, or do anything else, either … the loss of any restrictions there could be problematic.
If we had biological immortality, the ONLY way you could die since aging and disease are off the table, is by accident. So maybe everyone would become very risk averse, even pathologically so. But I kind of doubt it – it’s not like humans are known for thinking through all the ramifications of everything. Still … if the main threat vector is mishaps like car accidents maybe that would influence many people’s life choices.
Just FWIW speculation, since we’re playing mind games here.
to end that sentence…” particularly in the US where there is active sabotage of the science behind vaccines”