Or alternatively, a stratum of leadership class who actually worry about problems coming 100 years down the line because they fully expect to be effected by them.

I'm all for longetivity, but I admit what he said has substance.

It's not (only) about old people having short term vision/not enough time for reeducation.

25 or 30 year old people are already very often set in stone and unable to change their views and they have most of their life ahead of them.

Why not die at 30 then in the spirit of societal progress?

This argument is philosophical i.e. worthless. We will actually have to win with death to answer the question if it's good or not. It's not something you can figure out without doing it.

Raising children (and later, grandchildren) is the obvious answer.

Why not grand-grand-children? Current point looks like optimum, but it's really arbitrary and imposed only by external constraint of length of human life.

Well, Elon is working on building tunnels and (maze) cars, I guess if Mars doesn't work out, we can have Logan's Run.

We could have blinking red lights in our palms for that occasion

I generally agree with you, except for the view on class mobility. If we defeat aging altogether, I strongly suspect society to stratify aggressively between those that can afford it and those who can't, and worse, a class of immortal wealth to form. Today, maintaining generational wealth requires A) balancing relatively small family sizes to keep the exponential growth of family members relatively inline with the exponential growth of well-managed wealth against dying off because no one had kids and B) a mostly continuous line of responsible investors. In a future where dying of old age isn't a problem, A becomes much easier and B) is eliminated entirely. It's all the problems of generational wealth with none of the saving graces.

On the whole I think it's worth it, but it will definitely exasperate the problems already inherent to our economic system.

Max Planck said that science advances one funeral at a time