Old Age

I don't need to prove that our culture is obsessed with staying young and prolonging life. When I come back from Africa I can tell some stories that will shock you with the amount of contrast on that point, but I think we all know without being told that the obsession exists. What does the Bible have to say about this?
I was reading Deuteronomy 34. This is the chapter in which Moses finally dies at the age of 120. It says that Moses remained vigorous until the day of his death. He died because it was his time, not because his body failed. He was succeeded by Joshua, who was in his late 40s at least. It was at this point that he BEGAN his military career. He died at the age of 110. His companion Caleb, the same age, led the tribe of Judah in a resounding campaign in the promised land and apparently died at about the same age.
This was not a point in history where it was normal for people to live long. These men spent most of their lives in the desert. Their diet was far from meeting food pyramid specifications. They didn't have medicine, pacemakers, or wet wipes. And they sure as heck didn't "take it easy." How did they survive? I believe the answer is as straightforward as it is hard for Americans to swallow: God wanted them alive.
Look, when it comes right down to it, God is the one who makes sure that my heart will contract .98 seconds from now, and then do so again .98 seconds later. And that is why I am not super worried about my health or how long I live. I believe that we are to be good stewards of the body God gave us. I try to eat healthy and stay somewhat in shape. But I refuse to worry and obsess and waste kingdom resources in an effort to ward off the effects of sickness, aging, and a fallen world. Jesus told us to seek first the kingdom of God, and "all these things will be added to you." Based on the stories of Moses, Joshua, and Caleb, I think our health should be included in the "all these things."
As I have said before, God will provide the resources to accomplish His will. If we are doing His will, we are one of His resources. This doesn't mean we will necessarily live until 120 like Moses. I think it does guarantee that we are not going to die until we have either rejected His purposes for our life or fulfilled them. The next step is being okay with the concept that perhaps His purposes for my life will be fulfilled tomorrow.