Five years from now, it will be possible to take a trip overseas to have most of the senescent cells that have built up in your tissues cleared away via some form of drug or gene therapy treatment. That will reduce your risk of suffering most age-related diseases, and in fact make you measurably younger - it is a narrow form of rejuvenation, targeting just one of the various forms of cell and tissue damage that cause aging, age-related disease, and ultimately death. I say five years and mean it. If both of the present senescent cell clearance startup companies Oisin Biotechnologies and UNITY Biotechnology fail rather than succeed, and it is worth noting that the Oisin founders have a therapy that actually works in animal studies, while drugs and other approaches have also been shown to both clear senescent cells and extend life in mice, then there will be other attempts soon thereafter. The basic science of senescent cell clearance is completely open, and anyone can join in - in fact the successful crowdfunding of the first Major Mouse Testing Program study earlier this year was exactly that, citizen scientists joining in to advance the state of the art in this field.
Five years from now, however, there will be no definitive proof that senescent cell clearance extends life in humans, nor that it reduces risk of age-related disease in our species over the longer term. There will no doubt be a few more studies in mice showing life extension. There will be initial human evidence that clearance of senescent cells causes short-term improvements in technical biomarkers of aging such as DNA methylation patterns, or more easily assessed items such as skin condition - given how much of the skin in old people is made up of senescent cells - or markers of chronic inflammation. These are all compelling reasons to undertake the treatment, but if you want definite proof of life extension you'll have to wait a decade or more beyond the point of first availability, as that is about as long as it takes to put together and run academic studies that make a decent stab at quantifying effects on mortality in old people.
Uncertainty is the state of affairs when considering the effects of potentially life-extending therapies on human life span. Consider the practice of calorie restriction, for example, where theory suggests the likely outcome is a few extra years, but certainly not a large number of extra years or else it would be very apparent in epidemiological data. I think that an enterprising individual could, given a good relationship with the Calorie Restriction Society, put together a 20-year or 40-year study to that would - in theory - produce a decent set of data on practitioners and outcomes in the wild. It won't happen, most likely, because for one the funding isn't there for such a study, and secondly we'll be well into the era of widely available rejuvenation therapies along the way. Those calorie restriction practitioners will be taking advantage of treatments to repair the causes of aging just like everyone else.
Further, consider the possible effects of bisphosphonate treatment. There is some suggestion that this could add five years to life expectancy, a huge effect to go otherwise unnoticed for a treatment that quite a lot of people undergo in old age - but that may be exactly what has happened, for all we know. There is little work on replication or investigation, sadly. I point this out as an example of the degree to which uncertainty can and does exist for human data, as well as just how hard and expensive it is to dispel. It would take a large study, a lot of work, and waiting for a decade or so to figure out whether this bisphosphonate effect is real.
Now, consider that five years of additional life is not so far off a realistic expectation for the first prototype of any SENS-style rejuvenation therapy, such as senescent cell clearance, that repairs just one of the forms of damage that cause aging. Fixing one thing only gets you so far, as all the other forms of damage will still, on their own, kill you. Aubrey de Grey of the SENS Research Foundation believes that only small gains in overall life span are possible without addressing all of the causes of aging. This is a position well supported by statistical evidence for what would happen if, say, all cardiovascular disease or all cancer was eliminated without affecting other age-related disease. Only a few years of life expectancy would be gained in either of those cases. Arguments against that position run along the lines of suggesting that any repair of damage should produce incremental increases in life span, with reference to reliability theory, or that since all forms of damage and disease interact with one another, removing one will tend to slow the others. But we really won't know for sure until these therapies are out there in use and data is being gathered. You can only go so far in mice, especially given that their life spans are very much more plastic in response to circumstances than ours.
The reason I point out all of this is to note that the next couple of decades are going to be an increasingly confusing time for people who want to purchase elective therapies to extend healthy life. Things that actually work to a significant degree are going to be available alongside increasingly effective stem cell therapies and the same old garbage from the "anti-aging" marketplace that does absolutely nothing but part fools from their money. There will be infinite shades of grey between all of those things. You only have to look at the opportunists selling supposed longevity-enhancing supplements today based on calorie restriction mimetic research, and the articles in which that research is presented as equivalent and equal to SENS rejuvenation research approaches such as clearing senescent cells, to see how this is going to go. To navigate this near future market, for the decade or two it will take for the approaches that actually work to definitively prove their worth in human studies, you must understand more of the underlying science. You must be able to explain to yourself why damage repair approaches like those of the SENS portfolio are more likely to be effective than calorie restriction mimetic supplements - in short, your participation in the market will be guided by your take on the science. This is far from an academic exercise; time matters greatly.