Nevertheless, I think we can compute a rough estimate of how long a person could expect to live if old age were no longer inevitably fatal. Let’s give the OP a little satisfaction, at least. I will make all sorts of simplifying assumptions here which I’ll try to summarize later. (One of those assumptions is that we can even know what all the assumptions are.)
If there’s a probability P of dying in any given year, then the probability of surviving the year is 1 - P. Moreover, the probability of you surviving Y years is (1-P)^Y – that is, (1-P) to the power of Y. This quantity can also be viewed as the proportion of a large population that would still be alive after Y years.
This is an exponential “decay” function, much like the one that describes radioactive decay. You can even compute the “half-life” of an immortal human population by solving the equation (1-P)^Y = 1/2 for Y. If you do, you get the expression:
Y<half-life> = ln(1/2) / ln(1-P)
where “ln” is the natural, e-based logarithm. If we make the additional simplifying assumption that P is much much smaller than 1, then the above can be well approximated as Y<half-life> ~= ln(1/2)/(-P) = ln(2)/P = 0.693/P. Let’s call this half-life your expected lifespan – the number of years you can reasonably hope to live, knock on wood.
Now you just need a value for P, the annual death rate. I just happen to have a URL for that: http://www.infoplease.com/ipa/A0005110.html
You – as in you, the OP – didn’t specify whether murder and disease were still concerns, or whether accidents are the only threat. If it’s only accidents (35.6 deaths per 100,000 people per year), then you’ll have an expected lifespan of about 1,950 years. If you add in the risk of murder, then you’re cut down to 1,660 years. If you’re also at risk for hypertensive renal disease, well then, you poor schmo, I’m sorry to say you’re down to a mere 1,430 years.
But let’s be more optimistic. Say you move to Manitoba, keep in good shape, visit a doctor every year, get reliable cures for whatever ails ya, drive very little, and are extra cautious around household appliances. In other words, let’s say accidents are your only threat, and that through meticulous caution you are able to lower the accident risk by a factor of oh, maybe five? In this scenario, your expected lifespan grows to 9,730 years – about ten millenia.
Putting it big-picture terms: you might reasonably expect to live for a few thousand years. You’ve got a shot at ten thousand. Hardly a chance in hell though that you’ll make it to a hundred thousand or more, even in the best of circumstances.
All of this analysis works under the following assumptions:
[li]Your death rate is not changing remarkably from year to year.[/li][li]The probability of dying from two or more causes at the same time is negligible. (I.e. the causes are independent of each other.)[/li][li]The reference URL cites statistics only for the U.S., but there’s a lot of variation in the world at large of course, and even within the U.S. (Maybe we Americans are recklessly clumsy.)[/li][li]As Bryan mentions, there are effects from such extended life for which medical science presently has no cure. I’m assuming away this minor problem.[/li][/ul]
But best of luck on your journey through eternity! Don’t count on Social Security after the first couple centuries though.