Quality of life is clearly subjective and normative. It also represents an optimized balance of conflicting wants. In other words, economics rears its ugly head.
I just read an essay on quality of life by Chris Lucas. It's at the web site of the Calresco organization, which appears to be dedicated to the theory of multi objective optimization, of all things. Here is a link to the essay:
Before Darwin gave us 'natural selection' many theories of <A href="http://www.calresco.org/lucas/fitness.htm">fitness</A> had been proposed, these mostly derived from <A href="http://www.calresco.org/lucas/context.htm">ethics</A> and were variants on the question "what is the good life ?". Neo-Darwinism answers this only by saying 'survival', a one-dimensional reduction that <A href="http://www.calresco.org/emerge.htm">trivialises</A> life and cannot distinguish bacteria or virus from human or sequoia tree. Here we will say that fitness or 'Quality of Life' is a multidimensional set of [values], unique to each organism, person and context.