Concerning the average life expectancy:
I took a class on medieval Europe, and the professor had written his own books on the subject matter. One of the main issues he had with "mainstream" history was that it failed to distinguish between what health was like in medieval towns and cities, compared to villages and farms. Anyway, his main point on that was that in reality, the terrible hygiene in cities and large towns would indeed lower life expectancy, but that was normally only so for the common man. Also, people in towns, villages, farms, etc. did really live pretty healthy lives, barring the onset of plagues, injuries and death in childbirth. I fact, just because we "live longer" today does not mean we are any healthier. When you take in to account that an apple from 100 years ago had 20 times the amount of nutrients of one today, and you expound that to all agricultural products, you find that people had access to better food in the past. We just have better medicine and antibiotics, but being alive is not the same as being healthy. Ask the average modern North American to put on armor and fight a battle at 55 years of age. I think we can all imagine the results.
The point is, a script that kills people off between the ages of 30-50 would not be very historical.