EXW Guangdong / FOB Shenzhen/Ningbo cost?

direct EXW/FOB shipping typically carries a 5-15 % premium over sea freight pricing, but you get 3-7 day delivery. Kexin includes first 3 months storage free, then USD 0.5/piece/month.

Can I split production between China stock and EXW Guangdong / FOB Shenzhen/Ningbo?