There are people whose brain activity has ceased, who survived and still consider themselves to be the same person.
If you think living forever is worth money, it's reasonable to sign up for cryonics even if it's unlikely to work, because the other options (being buried in a wooden box or burned to ashes) are considerably less likely to work.
It seems to me that "living forever" is a fairly inaccurate term to use, and the emotional impact from part of the reader's brain taking it literally would make many readers very sympathetic to your argument, more so than if you used an accurate term.
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: