It really does go beyond human survival in space. Albeit, that is paramount, but the science that can be gained beyond that, is what will measure the ISS as paramount. We'll see.

Surviving long durations in space seems to be the number one priority, but if the science that they will be conducting up there is to benefit us in the long run, does benefit us in the long run, then it will be worth it. Be it from experiments that will benefit us on Earth down to examining samples from Mars (one can only hope, etc.). Then, it will have filled it's goal.

As far as the science, you have to remember that the ISS is ultimately taking orders from those of us on Earth., i. e., how long can our paint color last; can we grow this and such on OG; photovoltaics, etc.