Both sides had chemical weapons in World War II; neither side used them. Yet WWII was a total war.

That is, MAD or something MAD-like can restrain use of particular weapons, even in a total war.

Most conventional strategists believe a nuclear war wouldn't need to last a decade, as both parties would destroy themselves. Given the heavy civilian casualties and the decimation on the economies and infrastructure, the cost of a nuclear war and mutually assured destruction (MAD) outweigh the potential benefits.