Sourdough

I started of as hobby baker (I learned a lot from your podcast, thank you). Now I am selling a few loaves online. 

I life in the Philippines. Flour and especially organic, low-gluten etc flour is very expensive and often not available.

Soon I want to import my own flour. That means I would get about 200 to 300 kg of flour at a time which need to last up to 4 months.  

How do I store that? How do professional baker store their flour. I doubt they keep it for so many months though.

Thanks for your help 

Andy