Since 2009 it's completely different... Bank of Japan was the only active Central Bank in the markets around that time, since 09 there's dozens of Central Banks active in markets with the green light to sustain at all cost, off the books if needed. Can there be sudden stock crashes ? Of course, UK crashing out of Europe, Australia's Lehman or China Minsky are events that can cause a sudden Crash near term. Pension funds are big into equities now, adding the need for CB's to maintain Markets. Big question is when the Japanese stop buying all the CLO's... I am all in on long PUTs, but it's clear a hard landing in Markets will only come from a serious geo political event and not a earnings recession/economy deterioration