Razzle, scientists are working on it. After all, until you're 30 or so your cells just keep on keeping on; when they die their replacements are just as good. But sometime after that they slowly start to fail. It's as if they gradually switch off. Scientists are trying to figure out how, and how to stop the switch-off. If our bodies don't run down for 30 or so years, why not 60 or 90? Apart from accidents and major illnesses, of course, there's no apparent reason why we shouldn't keep going indefinitely.