As I mentioned on another thread, this is exactly what I thought and said a few years ago. Now I figure it's more like this: Putting the right kind of gas and oil in my car is important, even if the car has lasted much longer than expected.
BTW, that other post lead me to an interesting thought. I've had a number of accidents, injuries, and diseases in my life which, had I lived in prehistoric/premedicine times, would have killed me at a young age.
But let's say I lived back then (transported back in time 10,000 years as an infant), and didn't have any of those. And let's say that I wasn't killed by a saber-toothed tiger or marauding tribe. I wouldn't be that different, genetically, from my caveman buddies.
Would I have lived to the age of 56? What would I look like?
From what I have read you likely would have lived to 56 if you made it through the illnesses and injuries. Just the odds of making it through those illnesses and injuries was slim.