When you have more to lose, you behave in a more civilized fashion. This is a fair theory to explain why - despite the industrialization of war and nationalism - violence has in fact decreased over recorded history, even over the past century. We have on balance become much wealthier, and that includes a wealth of healthy years in comparison to our ancestors. This alters the balance of risk and reward in favor of trade, cooperation, patience, peace, and long-term over short-term gains.
Can we expect this trend to continue? I don't see why not. We are nowhere near the point at which a near-certainty of future longevity stretches ahead for so far that it is pointless to plan: there are still retirement funds and a structure of life that focuses relentlessly on a beginning, an industrious middle, and an end. Talk to me again when centuries are on the table, and we'll see how people approach things then from the perspective of foresight and organization.
Here is an article that argues for the benefits of longevity from the point of view of civics and the practical philosophy of living one's live as best one can - with an look at what lies beneath everyday to decisions to be humane and cultivated:
A major benefit of longer lifespans is the cultivation of a wide array of virtues. Prudence and forethought are among the salutary attributes that the lengthening of human life expectancies - hopefully to the point of eliminating any fixed upper bound - would bring about. Living longer renders people more hesitant to risk their lives, for the simple reason that they have many more years to lose than their less technologically endowed ancestors.
This is not science fiction or mere speculation; we see it already. In the Western world, average life expectancies increased from the twenties and thirties in the Middle Ages to the early thirties circa 1800 to the late forties circa 1900 to the late seventies and early eighties in our time. As Steven Pinker writes in his magnum opus, The Better Angels of Our Nature, the overall trend in the Western world (in spite of temporary spikes of conflict, such as the World Wars) has been toward greater peace and increased reluctance of individuals to throw their lives away in armed struggles for geopolitical gain. Long-term declines in crime rates, automobile fatalities, and even smoking have accompanied (and contributed to) rises in life expectancy. Economic growth and improvements in the technologies of production help as well. If a person has not only life but material comfort to lose, this amplifies the reluctance to undertake physical risks even further.
When life is long and good, humans move up on the hierarchy of needs. Not starving today ceases to be a worry, as does not getting murdered tomorrow. The true creativity of human faculties can then be directed toward addressing the grand, far more interesting and technologically demanding, challenges of our existence on this Earth.
The less likely a failure is to rob one of opportunities forever, the more likely humans will be to pursue the method of iterative learning and to discover new insights and improved techniques through a beneficent trial-and-error process, whose worst downsides will have been curtailed through technology and ethics. Life extension will lead us to avoid and eliminate the risks that should not exist, while enabling us to safely pursue the risks that could benefit us if approached properly.
Of the virtues brought by greater longevity, greater prosperity and more rapid progress will do the most to shape our future for the better. We are a young species in the grand scheme of things, and there is much left to accomplish. Given success in rejuvenation biotechnology development of the sort undertaken by the SENS Research Foundation many of us alive today will live on to see a golden future in which we expand from this world to form a society of ageless trillions, wealthy beyond measure, and blessed with a near complete understanding of physics, chemistry, and biology. In the long term all that matters is knowledge and technology: everything else is fleeting, including our lives if we don't move rapidly enough towards practical rejuvenation treatments.