The truth is you have no idea. If you're morbid and enjoy reading tragic stories, you might have nevertheless noticed that the terminally ill, those infected with bizarre venereal diseases (or run-of-the-mill venereal diseases, or even run-of-the-mill venereal Covid), people given personal doomsday clocks by their doctors, and people condemned to death in exotic penal systems often pull through anyway. They live.
Why? Nine times out of ten, the odds are bullshit. That's why. You know this whenever you look in the mirror and see a miracle looking back, which is every time. Every singularity is as remarkable as it is improbable, and it's a straight-up miracle that you exist because you are that.
It's amazing that you have enormous student loans; can worry about paying taxes on time; can have an orgasm, even one with another person; can search on the internet for poems by John Donne, who lived 450 years ago, and find them in less than five seconds; and are reading this right now. Yes, a miracle, a completely improbable singularity, like a fat orange on a snowy day or a fire held in the hand. You're magic, kid.
So you simply do not know how long you've got, no matter the odds you're given or the conventional wisdom that says boo-this and blah-that. First tell me how magic works—i.e. why and how you exist—and then I'll be willing to accept some metric for longevity that doesn't have to do with actuarial computation and Big Gerontology. Don't swallow another protean manifestation of ghoulish capitalism that seeks to monetize everything, even life and death. Don't capitulate to capitalism.
Average lifespans are death propaganda. Don't drink that Kool-Aid. Live. Live long and motherfucking prosper. As Sly said, "You can make it if you try. Push a little harder. Think a little deeper. Don't let the plastic bring you down." And know that everything trying to harness your assumptions about your life, how long it will last, and how great it could still be is plastic above you. Highly profitable plastic, perhaps, but for someone who is not you.
Rather, with Donne, look at the years to come and say, "Twice or thrice had I lov'd thee,/ Before I knew thy face or name;/ So in a voice, so in a shapeless flame" come the angles of our nature, our better angels, our reflections in the mirror getting older, getting greyer, but still here. We're still kicking and we're unwilling to trade the uncertainties of decades to come for the quiet enjoyment of the grave.