The average lifespan has not changed much once you hit 18, but your chances of dieing between 30 and 40 have gone up where your chances of dieing between 60 and 70 have gone down. I need to find and old actuarial table from the 50's to show compare with today.

Edit: http://www.ssa.gov/OACT/STATS/table4c6.html

I should say the odds of hitting 100 from 1 are about the same but the odds of hitting 100 from 65 have increased.

Male death probability with some comments by me:

  01) 0.000513 
  06) 0.000182 
  11) 0.000104
  12) 0.000156	
  13) 0.000273  (wow big jump suicide?)
  14) 0.000435  (some car)
  18) 0.001061  (more car)
  21) 0.001361  (full car)
  23) 0.001438  (peak of early death risk)
  31) 0.001367  (still car)
  41) 0.002629  (start of heath issues?)
  51) 0.005657
  61) 0.012966
  71) 0.030131
  81) 0.075724  
  91) 0.199019  	
  101) 0.388563

PS: Old age is bad for your heath but 21 vs 31 is about the same because it's mostly accidental death aka car accidents. Just watch the increase from 14 till 23.