Somewhat mild but long bear markets showed up after 16 - 17 years of market consolidation in 1923, 1946, and 1982. 

The 1923 bear market was a fairly short 7 months to the 1923 low and it started after the index approached new highs but yet remained below .

The 1946 bear market started as the market broke out to a new highs of the previous decade.  It took 36 months to get to the 1949 low.

The 1982 bear market began a couple of months after the the market made all time highs. It took 21 months to get to the 1982 low.