To date God hasn't seen fit to reveal that to us. We have read of the unfathomable life spans of the patriarchs and also the amazing vitality of Moses.
Time flies, and our physical and mental abilities often fly with it.
An article in the January 16 issue of Science describes research that indicates life spans could possibly be lengthened. Each cell in our bodies has a finite number of times it will divide, until the dead cell cannot replace itself. Like a candle that burns to the end of its wick and goes out, as part of the telomere is lost with each division, eventually nothing is left to give more life. Scientists were able to create a situation in retinal pigment epithelial cells and foreskin fibroblasts which gave them longer telomeres. The result was that they divided vigorously and had at least twenty more doublings than those cells typically have.