From the FAQ:
Q: Where do I store my smoker?
A: The smoker should be kept in a dry and well ventilated location. If you have purchased a cover use it to protect your smoker when not in use, as well as your cart. Always unplug the smoker when not in use. We do not recommend storing your smoker outside without a cover.
I would also add to check for rodents and spiders periodically.