At the cost of less elderly who'll miss out on being reproductive die to all the spots already being taken. Achieving immortality would be robbing from your descendants what your ancestors bestowed.

I was responding to a specific point to which your response seems irrelevant.

If my kids, or their kids, or their kids, etc. ever wanted me to die in order to "bestow" them with something...well, too bad. I wish my grandparents, and their parents, etc. were alive today.

Space on earth is finite. And even if add more hypotheticals like us becoming an interstellar species (actually I'd wager that's less unlikely than overcoming aging), in absence of aging exponential breeding would eventually outpace even the fastest space frontier colonization imaginable.

Yeah, and if you go from 100 year lifespan to 300 years and survive the societal collapse, would you be happy then? What about in 300 years?

Eventually all the atoms we know and love will decay and "disappear."

Give me a few million years of life and I'll still have billions more to think about what to do in the event of a heat death of the universe.

About that exponential breeding thing, I’ve got some bad news. You’d better sit down…

Here's a little thought experiment: when a company has layoffs, do more young people or more old people get the axe?

If we get to a place where people can live healthy lives until they are 300 years old, why do you think someone who finished college 40 years ago will be more valuable for a company than a fresh graduate? Because nowadays we have exactly this setup minus the 300 year lifespan, and often times the company is happy to let go of the senior guy.

Not aging is not the same as being invincible. There would still be turn over. You can also legislate things like mandatory retirement from a position so that others get a chance to move up. The legal aspects of longevity are easy to solve compared to the task of curing aging.