That sounds like it is biased towards people who haven't lost their parents by age 40. For people (like me) who have lost a parent before hitting the age of 40 it becomes more real sooner.
I assume clarge1120 meant that people feel immortal until 40 because their body generally does not stop them from doing things until one’s 40s.
Hmm it seemed unclear. I guess I am totally unlucky as im 35 and my body is already acting that way.