On the other hand, Psalms 90:10 rather casually puts the normal lifespan at 70-80 years, just about where it is now. So if medicine is doing us so much good, howcome people aren't living any longer (or at least, dying of old age later) than they did in biblical times?
Because "Thy Word is Truth."
Ummm, actually they are. For starters, the current ~80 years is an average, whereas in Biblical times that was closer to the maximum, with the average being more on the order of 40 if one was lucky.
Second, improving medical technology is currently increasingly average lifespan by about 0.4 years every year i.e. for every year you live, your average lifespan just increased by almost half a year. People who are already old won't notice this much, but people who are young will live far beyond the current average lifespan based on that fact alone. And that rate is accelerating at its fastest pace in history. Every year that number creeps higher; in a dozen years or so, you'll gain one year in lifespan for every year you live on average, though again it will show up more in the younger generations. It is worth noting that for most of human history, the average lifespan extension rate was approximately zero.
For this reason, I can think of some ghastly scenarios which will make this pollyannaish view of advances in biological sciences a pipedream. People may try to live forever by monkeying with natural processes, but it will probably end up being a horror story.