The reality of death can be useful to appreciate life, but I don't believe it is necessary. I think a better way to look at this is by accepting that impermanence and change is woven into the fabric of the universe. We call the impermanence that leads to the cessation of the physical body 'death', but impermanence happens all around us all the time at many levels.

f anything, I think that we don't live long enough to learn what this life is all about. If we became immortal we would be given the time to wonder just what the eff is going on out there, or in our minds, until we have achieved some sort of resolution (enlightenment, in the Eastern traditions) and that is what truly leads to wisdom.