How far in advance does Disney announce the nighttime show times such as Star Wars fireworks and River of Life?
They have not announced any dates/times for Rivers of Life. It has been about 4-6 weeks for SW fireworks?
Rivers of Light is still a huge question mark; we don't even know when it is opening yet, let alone how many shows per night and what time they will be. Strong rumors indicate a grand opening in mid November with possible previews and "soft openings" a week or two prior to that. In any case, there will probably not be a lot of advance notice.
Here is my best "guess" on show times based on the "facts" that we do know and typical Disney logic, but no "inside information". It has to be "full dark" to run the show, therefore I would assume that the first show could not be much earlier than an hour after "official" sunset. As that is approximately 5:30 in December, that would make 6:30 the earliest; I doubt that they would have a show before 7:00 (or even 8:00) because of dinner hour conflicts. The show is supposed to run 20-25 minutes. It will take at least 30 min to clear the seating and get everyone in for the next show, so the minimum time between shows would seem to be an hour (and I think that's pushing it; 90 minutes would make more sense). I think 7:00, 8:30, and 10:00 (if running 3 shows) is the earliest likely schedule, but personally think the schedule would be shifted an hour later (it would have to be in the summer). It will be interesting to see how clear my crystal ball is once they release the official information...
They seem to be releasing the SW showtimes about a month in advance.