I don't think anybody wants to live forever in an old person's body. Frankly, I'm not interested in extending my lifespan unless I can stay young or regain youth.

Also, if you eliminate all the aging-related causes of death the average lifespan is still only like 1000 years or something. Nobody's getting eternity. And yeah, for the chance to make a big enough change of the right kind to society I would indeed give up a 1000-year lifespan. My memes have fully subjugated my genes, and I'm at peace with that.