Yep, Looks Like 135 Years

Zeus was a jealous god, prone to acts of deception in order to seduce beautiful gods and mortals, and he was not pleased with Eos's infatuation with a rival. In a classic Devil's Bargain, he granted Eos's wish -- literally. He made Tithonus immortal, but did not grant him eternal youth.

As Tithonus aged, he became increasingly debilitated and demented, eventually driving Eos to distraction with his constant babbling.

In this article, The Tithonus Option, Chris Lawson argues against the possibility of technology presenting us the awful scenario of extended lifespan but limited improvement in quality of life.

Using some pretty advanced math (death rate functions and simple scenario analysis) he concludes that even if you solved a whole bunch of problems, like cancer and heart disease, people would still have an upper limit of 135 years on the planet. Except for me. :-)