What do tv stations normally do with all the footage they broadcast?

All news footage is placed in the "Newsroom archives" as there are times when it may be reused at later dates (other news stories, end of year summaries, end of decade summaries etc). All live programmes are also archived as they too may be reused at a later date. All "Soaps" etc that have been shown on the station are archived as they are often shown as "repeats" Films and such that are used are archived because they will often repeat them at regular intervals on the same station or on "sister stations".

i know that the bbc archives all footage due to digitization storing it is much simpler, also you have to remember that alot of that 24 hour broadcast is made up of adverts along with repeats of shows meaning a relativley small amount of media can be rebroadcast for years. i would say smaller stations probably have a few years limit after which they delete their stored data