Apple has added a new option for iTunes in the Cloud users, allowing them to defer large downloads of movies, TV shows, and music box sets for a later time. Currently, this new option does not work for apps, and is available only in places where iTunes in the Cloud is live. This option is available on iOS 6 and in iTunes 11, and can be used on things like whole seasons of television shows.
Clicking the Later button will not download any episodes. You'll be able to download your episodes at any time from iTunes in the Cloud.
When you purchase a television show or movie, you will be presented with three options for movie sets and TV seasons: Later, Download, and Download All. For individual episodes and movies, as well as music box sets, the Download All option is not present. This option is great if you find a TV season or collection of movies you want to buy, but you don't want to use up the space on your current device, or are on a cellular network with a data cap to worry about. You will find any items that you choose to download later in the Purchased section of the iTunes 11 store and the Purchased tab of the iOS 6 store.