In making a 40% rye, the pre-ferment sour I usually do is the following:

Rye Sour

• 360 g Medium rye flour (high quality organic works best)
• 360 g Water
• 20 g Rye sourdough starter (100% hydration)

Let sit at 78 degrees for 12 - 16 hours.

My question is, if I was to let this ferment for longer than 16 hours, is there a time amount that is too long?  I will not be able to get to it until it has been sitting for about 20 hours.

John