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I saw a short film online a few years ago that I'd like to watch again. I think the film itself is older - the video looked like it was ripped from VHS, and the special effects and production values were consistent with something made in the 80s or 90s. I don't think there were any computer graphics involved and it was probably shot on film. It was quite long for a short film, perhaps about 40 minutes in length. I'm fairly sure it was posted on Boing Boing, but I can't find the post.
The plot was that some people were stuck on a planet where people are born, grow old, and die within a very short space of time. (I can't remember how long - perhaps days or weeks, although it might be longer given that they could all learn how to speak.) To escape, somebody had to go on some kind of quest, which they'd been training for for generations, presumably because it was hard to complete before reaching the end of one's lifespan.
One scene in particular was a special effects sequence involving a pyramid with a set of moons orbiting a planet behind it - that sequence stuck in my mind.
It seems quite likely that the plot was based on a short story, in which case knowing the title of the short story would be helpful in tracking down the film.