In my opinion, it's not any more healthy to never think about death, to live in denial and pretend it doesn't exist. Moses prayed, "Lord teach us to number our days that we may gain a heart of wisdom." I believe it is healthy to assess our life every now and then, to look at how we've spent our time, to use wisely what we have left, assuming we live an "average" life span. No, we don't have any control over when we die, but we do have some control over how we live. I may be taking some points of my own world view for granted here, but I thought all human beings wanted purpose and meaning in their lives.
I don't know if you've ever heard of the young man from Australia, Nick Vujicic, who was born without limbs, but I just heard him on the radio yesterday, and he made this very profound statement: "Life without purpose is life without meaning, and life without meaning is life without hope."
The reason it is good to consider the brevity of our lives is so that we may choose to have purpose and meaning, and to do something good with our lives.