READ THIS:
This is going to show you how you can store a huge amount of items on a character for 30 days. The best part of this is that you don't need the mule you will be using in a city, you don't need it to join a guild, and you don't need it to have more bank tabs.
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What you may not know, is that the Mailbox in the game has basically infinite space. It can contain hundreds and thousands of items and letters. What you also probably don't know, is that if you send an item or items in the mail to a character, and the character does not open the mail, and then the character is deleted, the mail is sent back to you. Wow... that put a nice idea in my mind.
So, basically you make a mule toon, you don't even need it in a city, and you just mail shitloads of stuff you'll need later. Then, after a few weeks (maximum of thirty days, because mail is trashed automatically after thirty days) delete the toon, and you will get your mail back.
Another thing to note, is that if you think it will take too long to get all the mail out once you delete the toon, get an addon like Postal.
If you think that you won't have enough space in yours bags/bank, then remember, even the feature that requires you to only be able to take out or view 50 letters at once also has an effect on Postal. The addon will only take out 50 letters at once. Or you can check off which letters you want and don't want at that moment, and have the addon pull out only the ones you want.