Could the USSR have won a prolonged Hot War in Europe?

[aspqrz]

Back in the day, I would have said no, though I also would have said the war would inevitably go nuclear when one side or the other felt they were losing.

Since then we have had the shortcomings of the NATO, US, Warsaw Pact and Soviet forces increasingly brought to light, many of which ordinary punters had little way of sussing out back then.

So, purely as a mater of interest, and assuming that the Soviet planners' fantasy on being on the banks of the Rhine at D+5 (or whatever it was) was, indeed, a fantasy ... and that the NATO planners' fantasy of stopping the Soviets more or less dead in their tracks was, indeed, also a fantasy ... I am asking the following ...

Could the USSR have won a prolonged and entirely conventional war primarily fought in Europe and its peripheries?

Feel free to parse your answers/opinions/arguments by decade - 50s, 60s, 70s and 80s - but base them on what we know now, not what we thought we knew back then.

Note: I really don't have an axe to grind here ... my suspicion is that the Soviets couldn't have sustained a long duration war, and didn't have a high probability of achieving the quick victory they seemed to have planned for, but I'm not wedded to the idea.

I suppose a corollary to the basic question is ...

Could a conventional war primarily fought in Europe and its peripheries have avoided going nuclear, and for how long?

('peripheries' implies the Mediterranean, North Atlantic, Middle East etc. but feel free to parse it with any limits or expansions you feel realistic and/or inevitable)

As a child of the era, I don't believe it could have been avoided ... and there is evidence to suggest the Soviets didn't, either (though it probably isn't, and probably can't be, conclusive with the information at hand here and now) ... though I felt there was a possibility (of unspecified level of probability, but significantly greater than zero) that it may not have devolved into 'War Games' like 'Global Thermonuclear War.'

Ideas? Opinions?

Phil