The jump from "could" to "should" seems questionable at best. What's so great about the rich elite living to be 200 years old? Would you like a bunch of people from the 19th century still around, influencing politicians with their money today? It would slow down the rate of social progress. It would also increase wealth inequality, since money hoarded by one generation tends to be squandered by the subsequent. There's also an argument to be made that science advances one funeral at a time; keeping people around loong after their expiration date would likely slow down the rate of scientific progress as well.
There are other reasons for longer lifespans, but you’re implicitly saying all of them combined are not enough to counter the reasons you give.
Now, I’m not certain either way about the broader social impacts — I personally very much want to live longer, and yet I am also aware that my personal interests are not always aligned with group interests, e.g. tragedy of commons, Nash equilibrium, prisoners’ dilemma — but it is extremely unlikely that any negative consequences are perfectly balanced to positives either personally or collectively, so I am absolutely certain that the one thing we should not do is leave lifespan as is.
That’s fine, but not what you wrote before.
> This technology has substantial potential for social harm
Yup, like everything.
> and should not be pursued until all of those concerns are addressed.
Nope.
Because death itself has direct harm — indeed, it is widely regarded as the either the worst or among the worst things one person can do to another — the burden of proof is on those who say it would be bad to delay death as much as possible.
I mean, we already delay death as much as possible with all kinds of medical interventions.
You just described "Vampire: The Masquerade"