I couldn't improve upon Midpack's post #5 as an initial answer to your question.
However, I will add a couple of random points for your consideration:
* If you haven't already, you might like to read bogleheads.org especially the wiki and recommended reading list... this will generally be data to support inability of the vast majority to consistently time the market. Perma bears will always call crashes (but have a lot of false negatives and not call market re-entry timing) and vice versa.
* IMHO I am pretty confident (and probably in agreement with you) that returns for the S&P, small cap, REIT we have experienced since Mar 6 2009 will not continue at the same compound annual growth rate for the next 100, 50, 20 years.... 10, 5, 2, 1 I am less and less confident.
* If one is not a market timer... then any knowledge, understanding or belief about position in market cycles won't be actionable
* If one is worried about position in market cycle... I think Boglehead shorthand explanation for this might be that asset allocation risk is too high.
* Perhaps this might also be considered to be consistent with: if one is a little bit of a market timer... then perhaps they might nudge their asset allocation to less risk or less highly valued assets. At this time, it might be more cash, more short term bonds, less REIT
To be consistent, after a crash perhaps one would nudge allocation to more stocks, more REIT, less bonds.
[I think I might dabble here a little]
* IMHO Asset allocation primarily works (not saying it is the only way that works) because it forces you to sell high and buy low.... eg. stock portfolio might have dropped 55% during 2008-9 but if you maintained your REIT and stock allocation you would have been recovered+ in a year or so. What doesn't consistently work is changing allocation % on a
random feel/CNBC/seeking alpha post/technical indicator... as it might involve selling high but perhaps missing out on higher... then perhaps buying back in and perhaps crashing... and then perhaps not buying low.