On page 5 he says (in his narration) that he's 27, with that being past the age of one's prime.
Wut? That makes no sense.
That would only be the case if he wasn't exercising and had an unhealthy diet. Someone in his position and his lifestyle should reach his prime around 30-35 years old, and would only be truly past his prime once in his 40s.
Damn, it really felt weird seeing him refer to himself as an "old man".
Based on this and on the "past his prime" thing, I'm guessing that the author believes in the myth of the low life expectancy in the Middle Ages.
Thing is, that's just an average and it's only as low as it is BECAUSE of the high mortality rate of children. That's what brings the average down. However, the people who lived past the high mortality period usually lived pretty old, and even more so for the people who were richer(thus giving them more possibilities for a healthy lifestyle).
Back then, if someone lived past childhood, they were usually set to live up to at least their 60-70s(with some living into their late 80s, thought that was rarer), as long as they weren't killed.
Edit:
@Manakete Actually, the life expectancy thing you mentioned is a myth brought about by bad info being believed and then spread around. People didn't age faster in the Middle Ages. They didn't look like elderly people when only 45. Yet, there were still a lot of elderly people around. And that's just one example.
Edit2:
@Exeryon While what you said is mostly correct, there are still some things you got wrong. While it was often the case for people in their 40s to have grandchildren, that doesn't mean that they looked elderly. It's just that back then it was also normal for great-grandparents to be around, and from time to time great-great-grandparents were also around. Just because people often had children while younger doesn't mean that they age faster.
@FireCamp Actually, people in their 60s weren't rare in the Middle Ages at all.