The ego or spiritual journey has as one of its goals that you accept death, the transience of life.
This is one of the more vague pieces of the puzzle that doesn't readily make sense.
Ego is your sense of identity, the idea that you and I exist at all.
As you ascend to various levels, you have to give that identity up, giving up the idea that you have importance or relevance, or that your needs and desires matter.
You'll have a number of ego deaths and losses: rock bottom moments, break ups, job losses, divorces, bankruptcy, suicide and depression.
Each one you complete takes you closer and higher and eventually at the crossover point there is a final ego death. It's quite an experience.
In line with the ego deaths comes loss of attachment - to people, things, ideas, beliefs and eventually your identity.
The loss of attachment is designed to make it easier for you to move on, and goes hand in hand with ego deaths usually.
Life in retrospect
When you go through an experience it takes weeks. When you read a book about someone's experience it takes days, maybe weeks. A movie only takes a few hours though.
What this means is that you see the whole story, and so you get the big picture. The only thing that varies is the time elapsed.
Life on earth is like that - best understood retrospectively as a whole. The short duration is like watching a movie - it condenses the energy and story down over a brief period of time.
So the brevity of life has to do with quickly and efficiently producing advanced individuated souls. You get quick turnover in other words :)
Article on time and understanding time as a dimension: http://lifecoachestoolbox.com/index.php/key-spiritual-concepts-understanding-time-as-a-dimension