Rye sourdough - cold fermentation time

Hi all:

I'm making the Tartine Country Rye loaf with the following formula:

• Leaven: 20% 
• Hydration: 80% 
• Rye flour: 17% 
• Bread flour: 83%
• Salt: 2%

Can I cold ferment for final proof for around 18-20 hours, or is that too long?  

Thanks!