You can store an unlimited number of resources in your towns without resources!
When looking at your resource tiles (farms, sawmills, quarries, and mines) each one can store a certain amount of resources. In addition any warehouses you have can hold resources. HOWEVER you can go over this amount. Let’s say you have enough farms to hold 1.5 million food. I can go buy 9.999 million food on the market (the max I can buy at a time) and somehow my townspeople find places to store the food. It must be a bug in the game but using this method I can actually store an unlimited amount food so I don’t have to worry about feeding my army. I can actually store an unlimited amount of resources this way.
Another example would be when upgrading your walls to level 9 or level 10. Walls level 9 require 2.56 Million stone. Walls level 10 require 5.12 Million stone. I don’t have enough space to store that much stone, but using this flaw in the Evony game I can store extra stone by buying it on the market, transporting it in from another town, or stealing it from another player/barbarian.
Since I can store an unlimited amount of resources, why do I need warehouses?