Joke Answer: Kill myself right there. HA! Proved him wrong, didn't I! Unless I didn't die, in which case that means I have exactly 80 more years to live no matter what happens to me. Fuck yeah I'm invincible! for 80 years. Time to exploit this for all its worth.
Serious Answer: Business as usual. They might as well say this at birth, its so common for people to live to be 80. And even if right now I were to live 80 more years from this exact point that would only put me about 100. Which isn't that much more that 80. Although living an entire century would be cool...