As said above - inventory space will become an issue soon and even if you'll employ two available retainers you might eventually run out of space if you're hoarding type like me. As the game will not allow you to (directly) pass items on your own other characters on the same server to use them as mules (unles you're multiboxing) the only other "storage" option would be to establish your own FC mainly for the purpose of storring excessive amount of items and gathered or crafted materials.