In fact, I'll argue that any serious life extension will have to come with a similarly extended lease on quality. Senesence will need to be stemmed upstream, so more of your 120 years will be good years.
Imagine those at age 100 preparing for the second half of their lives rather than expecting to die in the very near future. That may spawn a new phase of maturation that doesn't exist today. What if, generations from now, people recall how young and dumb they were before they turned 100?
To give an example:
The fact that it might be impossible to "fix" aging is no reason to not fight against it. Just like the conservation of energy law and the 2nd law of thermodynamics are no reason for us not to try to inch closer and closer to the theoretical limits of efficiency in clean energy production.
A rose by any other name, is just as sweet. I mean to say, all of the STUFF associated with malady is there. So how / why does death/aging ... with all its symptoms ... differ?
It doesn't.
Life can be extended, perhaps. Made more productive, certainly. But a cure for death? Show me one organism in nature anywhere near as complex as a human being with the capacity for unlimited aging and I'll believe it's possible. Technologically extending life for a few decades on average with a battery of complex and expensive medical treatments is not a cure.
Otherwise, looking at death or aging as a disease, while it might provide the catalyst for any number of worthwhile medical advances, also provides false hope. It's like waiting for the Singularity to happen so we can all upload our minds into the Eschaton. It's just another form of hoping for an afterlife.
Yes, absolutely act as if it can be cured, but don't believe it can.