2 ________________________________ European Demographic Research Papers are working papers that deal with all-European issues or with issues that are important to a large number of countries. All contributions have received only limited review. Abstract Conventional indicators of human lifespan (Graunt 1661; Chiang 1984) are based on a hypothetical synthesis of the mortality conditions of different cohorts with (as yet) incomplete life histories. There is a considerable ongoing debate about improvements to the traditional methodology under changing mortality rates Here we show that both the centuries-long tradition of conventional lifespan indicators and the more recent criticism of them ignore the true exposures of individuals to prevailing mortality levels. These exposures form a genuine part of a more comprehensive picture of the prevailing mortality conditions. In low-mortality countries, our estimated duration of human life is about 95 years, which exceeds the conventional estimates by 15 years. This difference is crucial for health care, long-term care and pension systems. Our theory implies that mortality dynamics are characterised by considerable inertia. This is used to develop new effective methods of forecasting, leading to a more optimistic outlook for future mortality. Even if there were no further change in mortality conditions, conventional life expectancy at birth will rise to 90 years by 2050, while the probability to survive beyond age 100 will reach 30% in low-mortality countries. Conventional longevity indicators still provide a useful summary of the observed mortality rates which, in turn, are essential for population projections. However, they do not give the full picture of current mortality conditions and mislead about the prospects of human longevity.