I think they could last in some capacity if they win.
It‘s plausible that they commit genocide for living space on an unprecedented scale, killing over a hundred million for living space, and then change their minds. But I think that even though it will economically implode, once they have actually enslaved the survivors of Eastern Europe and moved millions of Germans out there, it seems hard to actually stop. They will have to be really committed by that point, to know what they have done and continued, will have millions living in Eastern Europe in possession of millions of slaves, and will idolize Hitler as a conqueror on par with Khan or Alexander.
Will they really call it quits after all of that?
Unlike Italian Fascism (which to me seems like a fad bound to either revert to Democracy, revert to Monarchism, or fall to Socialism), Nazism seems like a much more revolutionary system that will change the way people think on a different level. When Nazism triggers an economic collapse, that might just make convincing people to move to Eastern Europe and live off of hundreds or thousands of free acres of land with your own slave easier, as the modern economy will be worse.
It won’t be the same Nazi Germany as Germany wasn’t North Korea or Pagan, but I can see a giant Germany turning into a Pagan North Korea, or something akin to modern China.