A Wild Yeast sourdough starter gives you a lifetime supply of yeast for baking. If you ever are not planning on using any of your Wild Yeast within the next week or so, or you just want to have a back up (in case you forget about your starter in the corner of your kitchen and it goes bad or some other catastrophe strikes) you may want to think about long term storage.
Short Long Term
If you think you will use your starter again within the next few months you can cover with plastic and set in the back corner of your fridge. Remove the starter once a week and feed to roughly double the starter. Store this way for up to two months.
Long Long Term
If you don't plan on using your starter again for a number of months you can freeze your starter up to six months. If you want to store longer than this, pull it out refresh it by feeding it a few days, and then refreeze.
Alternately you can dry the starter (like the Wild Yeast sourdough starter spoons are). You can then reconstitute later with warm water. It may last a very long time this way, however, it could be susceptible to going bad depending on how dry it its stored. I would not suggest this method of storage for longer than 6 months.