This leaves me with the impression of numeric legerdemain. Start by bringing up that old chestnut - decades to recover from the 1929 stock market crash to scare you, and then palm it - don't use that crash when looking at market returns. We don't want you to get too scared.
How long did it really take to recover, considering deflation (in the 30s) and dividends? Mark Hulbert wrote this article in the NYTimes, entitled: "
25 Years to Bounce Back? Try 4½"
Even using raw stock prices, that's 2
5 years for the Dow (Nov 23, 19
54) per Hulbert, or about 30 years
inflation adjusted, or 2
5 years for the S&P
500 (
Shiller data) or 26 years
inflation adjusted. It looks like the 28 year figure was pulled out of a hat.

He says that "Starting in 1941 still encompasses a large part of those dark days in the market, and World War II". But by starting in 1941 (so that the initial high water mark is Jan 2, 1941), many of those "dark days", especially between 1943 and 1946 appear to be "happy" or "benign" days (new high water mark or within
5% of the most recent high).
Watch him turn dark nights into bright days.
Taking days at random strikes me as dubious. What's the chance that a day will be within
5% of the most recent high? Very good if the previous day was. Likewise, if yesterday the market was down 40%+ from its high, then the chances are much better that it will be down 40%+ tomorrow than if the market just hit a new high (it has never fallen 40% in a single day). While each day's movement may be random, one day's price is usually pretty close to the previous day's.
Certain things are obvious. Since the market has an upward bias, it will spend more time near highs than near lows. Just as obvious is that
new highs will bunch - you're not going to hit a new high unless you're currently at or near a high. 2017 was a good example.
What are the odds of falling into a bear market if the market is already in a correction? Better than if it's hitting new highs. That's also obvious because it has a lot less to fall (a bear must begin as a correction). Conversely, if you're already in a bear market, what are the odds of entering a "second" bear market (i.e. falling 20% more)? Pretty small, because rarely does the market drop 40% or more.
So making use of any of this is tricky - too slow a trigger and you may smooth things out (miss the very bottom) but risk missing the rebound; too fast a trigger and you may get faked out and miss a rising market because it dipped for a week or a month.