A serious question as to the whole cliche as of "what if the Cold War was between the US and Britain and the Soviet Union, rather than US and Britain and Germany?"
But something I rarely see is any sort of attempt to accurately guess as to how long a victorious Soviet Union could stand. The "Thousand Year Reich" was only on the cutting edge for a few decades before it's older scientists were replaced by military-trained youths of Hitler's education system, and even before then the economy was heading into the crash of the 70's.
But what about the Soviets? There's the Siberian Resource Region of lots of gold and oil, a victorious Soviet Union would conceivably be able to loot more of Europe than Germany could (if only because Germany wouldn't loot itself), and so would have its own resource-exports. With rich raw materials, could it have survived longer?