I voted for never, because revolutions don't really change anything. At least not the type generally thought of as revolutions - i.e. violent overthrowing of current governments.
I just watched this awesome movie,
The Gladiators (The Peace Game), or in it's native tongue
Gladiatorerna by British expatriate director
Peter Watkins. This film won the Grand Prix at the Trieste International Science Fiction Film Festival, presumably in 1969 when it was released.
The basic concept of the movie is that the UN has decided that, in order to prevent World War III, it will turn warfare into a televised battle between small groups refereed by a computer. I didn't even realize how old this movie was until I was well into it, and it is surprisingly undated as well as prophetic (there wasn't much reality television besides Candid Camera back in '69, but today this seems spookily believable.) The one thing that most notably does date it is that the computer was represented by the classic IBM typewriter ball, but that still worked pretty well.
Anyway, there's a French soldier/game player who is dead set to be the first into "The Control Room" where he hopes to destroy the system and free everyone from it. He does get there, but then is asked what he will put in place of the system, and the best he can offer? A new system. The generals were much more threatened by two soldiers, a Brit and a Chinese Communist, who fall in love. But they had them beat to death by police.