I personally do not count anything that has happened since then as an end of that peace - never were major great powers in direct shooting (vaporizing?) conflict over extended periods.
I attribute the length of the period to a number of things. Firstly, from the moment we nuked Japan, we feared great war so strongly, that we exhibited many behaviors that were not, from a historical perspective, at all normal. Appeasement, truce calling, detente, ongoing negotiations with no conclusive end point, etc. I issue no value judgement regarding those behaviors, I only am bringing them to light.
Secondly, we took the UN much more seriously than the League of Nations or any other earlier international body. In many if not most cases, much of our support of and engagement with the UN has been overtly antithetical to our true national interest; we have, in essence, taken the anti Clausewitzian approach. This is, in a way, another manifestation of the first item - our now near primal fear of great war (even, I might add, to the point of refusal to consider it in cases where, from a perspective of the long term survival of Western Civilization, it would have been the correct, ableit exceedingly painful, decision).
Thirdly, the advanced state of decay of the age old aristocratic structures, and, innate Judeo Christian Western institutions, fomented by the increasing influence of anti traditional intellectuals brought on by inexpensive media means, the bourgeiosification of higher education and the previously mentioned efforts to discredit Von Clausewitz' theses, resulted in a potent Leftist polity throughout the West with its own ill effects.
And finally, the change in monetary policy from one of relatively fixed (or at best, slowly changing and metal backed) money supply to one of elasticity and bourgeiosified debt incursion, gave rise to the historically unprecedented and unproven hyper commercial orientation of Western modernism. This last item clearly drives the mentality of the so called "free traders." Certainly it comes as no surprise that when that mentality is juxtaposed upon the first three factors, the current state of affairs is a predictable outcome.
Given that none of these four factors have a deep foundation and are certainly not part of the thousand plus year old underpinnings of the core of Western Civilization, any claim as to their stability and staying power must be suspect.