I've always pondered this, as people often take the Middle Ages still as a dark time, where most to everything was cut off to a given degree. I realize now that to some extent, this is wrong, but it makes me question if the medicine at the time was still good. This is because I'm under the guise that until Germ Theory, survival chances from anything such is surgery in time of war: Things kind of died and mostly from infections contracted.
We talked about some similar questions last week in this thread. It doesn't completely answer your question, but it might be a helpful start for you while you wait for others to answer you here.
This is a very interesting question because you just reminded me of Usama ibn Munqidh, a veteran Muslim soldier who survived till old age, he was active during the Crusades and served many kingdoms and dynasties in Middle East.
Here is an excerpt from a book called Saracen Faris AD 1050-1250 (Warrior) p.57
"A successful soldier could retire in respect and perhaps prosperity. Those that survived could also hope to reach a good age as the diet and more hygienic conditions of medieval; Islamic culture seems to have led to a longer life-span than the normal in Europe. Many men from the educated elite took up writing a fair amount of poetry while serving as soldiers, just as Usama did. Others seem to have trained younger soldiers or took up civilians career as merchants. Business and trade were perfectly honourable professions; the profit motive was not see in the dubious light as it was in Christian Europe."