re: #25 Quoth the raven, Covfefe.

As another example, NASA recycled the media for the Apollo 11 mission (!) sometime in the Space Shuttle era. The original TV broadcast tapes, however, were archived and intact.

You are correct. They keep a lot of stuff, so much stuff that the archiving itself has become news stories. It was interesting that you mentioned Doctor Who. I just found wikipedia article on the fact that there are missing episodes of the show:

Numerous portions of the long-running British science-fiction television programme Doctor Who are no longer held by the BBC. Between 1967 and 1978 the BBC routinely deleted archive programmes, for various practical reasons (lack of space, scarcity of materials, a lack of rebroadcast rights).[1] As a result of the cull, 97 of 253 episodes from the programme’s first six years are currently missing, primarily from seasons 3 through 5, leaving 26 serials incomplete. Many more were considered lost until recovered from various sources, mostly overseas broadcasters.

Doctor Who is not unique in its losses, as many broadcasters regularly cleared their archives in this manner. Until the BBC changed its archiving policy in 1978, thousands of hours of programming, in all genres, were deleted. Other affected BBC series include Dad’s Army, Z-Cars, The Wednesday Play, Steptoe and Son, and Not Only… But Also.[2] ITV regional franchises also deleted many programmes, including early videotaped episodes of The Avengers.[3]

Doctor Who is unusual, however, in that each of its 97 missing episodes survives in audio form, recorded off-air by fans at home.[4] Most episodes are also represented by production stills, telesnaps, or short video clips. Furthermore, after careful restoration, all 1970s episodes exist in full colour, which is not always the case for other series.