Living kills us.
Basically every thing we do slowly kills us. Our bodies are slowly dying since we're born, and the deeper you dig into the science of everything we do, inhale, eat, etc, the more you realize everything has a downside.
On a DNA level our telomeres-the ends of chromosomes that keep them stable-shorten as we live, and though slowing that is possible we have found no way to reverse it. So no matter how healthy you eat, exercise, avoid stress, etc, it's inevitable.
Makes it seem pretty silly then to hyper focus all our decisions on whether they'll kill us when existing is killing us.
One theoretical approach to completely halt telomere shortening would involve perpetual activation of telomerase, the enzyme responsible for adding DNA sequences to the ends of chromosomes, effectively lengthening telomeres with each cell division. Additionally, developing strategies to prevent or repair DNA damage and enhance cellular health could potentially stop telomeres from shortening altogether. However, achieving this in practice remains a challenge, as it requires precise regulation of telomerase activity to avoid potential risks such as cancer development, as well as addressing other factors contributing to telomere attrition.
Further research is needed. This is currently an area of active research.
Replacing everything should be possible – first would be a mitochondrial replacement that would basically cut most aging processes to a few percent of what they are now, and then massive injections of stem cells coupled by drugs to get rid of senescent cells.
I picture the process of being taking multiple current mitochondria, sequencing them to figure out, and then re-create what the original mitochondria you inherited were like, replicating those new "original" mitochondria, packaging them in tailored stem cells, and letting the stem cells inject them into your cells.
A similar process would be applied to stem cells; multiple current cells from various organs would be sequenced to re-create your original pluripotent stem cells, probably with a few enhancements such as ramping up repair mechanisms.
In both cases the body would do most of the work of replacement.
That still leaves long-lived cells like neurons to worry about, but at least those would be healthy due to the mitochondrial replacement.
Very likely we will upload our consciousness, but an alternative is that we will keep embedding hardware in our bodies until our bodies are no longer dominated by biology.
If you copied the connectivity between all cells in the brain, including the strength of the synapses, you would get something that was close enough to "you" that it would argue that it was you. The only advantage of moving the neurons is that it solves the problem of what to do with the original to avoid having two entities claiming to be the same person.
One thing to note, however, is that even if it starts as you, if the hardware is different it will learn very differently in the future from the way your current wetware would learn.
CRISPR technology is still in its infancy.
Personally, I do not entertain ideas of myself living forever, but I think it's important to maintain a healthy lifestyle, because that can be a very important factor in happiness is your physiology, and secondly, because I would like to have as good of an aging process as possible so that my quality of life does not deteriorate horribly within my control. Some things are out of your control, but you can certainly influence certain things as well.
I know a guy who is worth $2 billion and has two private jets, but he can't even enjoy his wealth because he's so overweight and so unhealthy that he's always bedridden. Health is the foundation.