Bulk fermentation is the rise after mixing, and its single most important variable is temperature, not hours. A degree or two of dough temperature changes yeast activity dramatically: the rate roughly doubles with each 8 to 10 degrees Celsius increase.
Aim for dough at 24 to 26 degrees for most lean breads, which at typical room temperatures means using water around 30 degrees in winter and cool tap water in summer. Measure the dough temperature, not the air, with a probe a few minutes after mixing.
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Judge the end of bulk by volume, not the clock: about 50 percent increase for pan loaves and focaccia, and 30 to 50 percent for rustic breads that will get a long shaped proof. Warm, fast doughs taste blunter; cool, slow doughs taste fuller.