Death Gives Meaning to Life?

A (very brief) synopsis of one of the thoughts/musings that has transcribed a path through my mind today.

Death Gives Meaning to Life?

I cannot count the times I have heard this phrase uttered by scholars and pundits, including Bill McKibben, Daniel Callahan, and Leon Kass (if anyone wants any references, I can find articles/books by these authors which refer to this issue).  They argue against pursuing radical life span extension because it will make life boring and/or meaningless by removing this tenet.  Is their hypothesis correct?

I am not sure that we can even radically extend human lifespans; I am highly skeptical that this phenomenon will occur in my lifetime.  Regardless, I do not think that human beings' lives will suddenly be bereft of meaning if their maximum lifespans increased from the current 90-120 years to centuries.  People will simply set artificial deadlines and use these limits to guide their behaviors and decisions.  We already do it now.  How many times have we heard someone say, "I want to achieve these goals by the time I'm..." 20 or 30 or 40 (or whatever age)?  Their timetable may or may not be dependent on aging; however, it is unlikely due to any worries about dying (especially for people in their teens and twenties who utter these pronouncements).

I'm sure that some proponents of radical lifespan extension or perhaps even some detractors have noted this fact; however, I can't think of anyone who has broached this hypothesis off-hand.  If readers can think of anyone who has proposed this view, let me know.