Question

How long can the human life span be extended?

Answer 1

you cannot extend human life, but the healthy people can live up to 120, though, that was a world record. to live that long and keep your sanity, your chances are very slim, but due to great increases in medical technology, if you don't smoke, don't do drugs and excessive alcohol, then you can expect to live a long life

Answer 2

Well, theoretically there are many ways to extend human life span. But most of them come with horrific side effects.
Best example: Removing the gene for programmed cell death. This would mean that cells in the body would live indefinitely. Unfortunately you would die of several cancers since apoptosis would not occur. So find an effective cure for cancer, and with a bit of genetic manipulation you can maybe live much longer.
Activation of genes changes throughout our lifespan. As we grow older, different genes activate, causing changes at a biochemical level in our bodies. In that sense, it is possible to 'fool' the body into stopping these activations, therefore extending your life. Identify the genes that cause these changes, and so long as they are not in charge of other physiological effects, you could switch them off, in essence fooling your body into believing that it is younger than it actually is.
Beyond these, nanomedicine and body part cloning can both play an effect in preventing age related illnesses, thereby slowing the ageing process.
Of course, all the above are theory.