That of course depends on who your audience is and what purpose you use the movie for. By that I mean, if I am doing animations for a game I save in eight or ten frames because eight frames is a walk cycle.
If I am going to use a movie on a slower computer, I might save it in 15 frames per second. A more powerful computer I would save in 24 or 30 frames. 24 frames per sec is movie film standard and 29.9 or 30 frames per sec is NTSC or television standard. SO, I usually try to match what may work best in any given situation. You have to experiment a bit to see what it looks and feels like. Sometimes it's too fast, sometimes too slow. The less frames per second the faster the animation.
Also just a side note: If you want your animation fully rendered you would render each frame individually, save each frame seperately, and then let quicktimePro put them together as an image sequence and save it as a quicktime movie. Takes a lot of patience and time to do but I don't know how else to get a fully rendered movie. Maybe Poser 5 will fix that?