What is the average life expectancy of a miner?

Depends on the period in history and the type of mining (tin, copper, slate, coal etc).

Around 1900 the average UK male life expectancy was 45years it is estimated that a miners life expectancy was decreased by 10 years (mining was one of the most dangerous jobs at the time). An average of over 1% of the mining workforce were killed annually in accidents and the rest through degenerative diseases.