I agree completely with what you say; with one proviso.
The prior periods you refer to, especially 74 etc, have one things that is different to today: no QE.
I dont know whats going to happen, but I'd venture a guess that QE is in a way smoothly out the troughs a bit and lengthening the cycle.
I'm in complete agreement with you, markets will mean-revert and it could get quite brutal. I so, however, suspect, it could be a while yet before they do.
I'm also sitting on 20% cash, but wont be spending it anytime soon, unless I see an obvious bargain.