life expectancy 
noun
The average period that a person may expect to live: the British male now has a life expectancy of 77.6 years figurative the improved life expectancy of modern cars...
- They are now of an age that exceeds the average life expectancy in the countries where they live.
- It's the risks relevant to the place where you currently live that affect your life expectancy while living there.
- One in five adults is HIV positive and the average life expectancy at birth is just under 49 years.