Natural in the context of not being murdered or otherwise unlucky. I really feel especially for say, kids who get terminal diseases before they reach their teens, so I'll throw that in. I'm not old yet, but I've gotten to experience a lot of life to the point where I'd accept my fate. Sorry for the nonanswer, but it requires a bit of thinking and opinion.

If medicine advanced to the point of repairing your body to be able to live a healthy life indefinitely would you try stay healthy using the best science has to offer or would you not?

It would depend on a lot of factors. Can everyone afford it, even my poorer friends and family? Is the population booming? Off the cuff - no. If we all lived forever there'd be no world change, the birth rate would have to drop by a ton to near zero, etc. The older I become, the more set in my ways I become. That's just natural, even if you consciously fight it. Imagine where we'd be as a society if they'd discovered how to live forever in the caveman days...

I understand your point of view however it leaves more questions than answers. For example at what point do you stop trying to stay healthy? Modern medicine and sanitation got us this far. Is it already too much?