Hi gnetzer
I personally believe the "magic number" is anywhere from
50-65 slides.
However, as with anything, the actual number will vary and
will depend on what exactly you are doing with your movie. For
example, you might be able to get away with as many as 100 slides
if your movie is pretty simple, having only text captions and no
audio. And you might also discover that a movie with only 50 slides
is really too large if it is crammed with tons of objects and lots
of audio.
I also believe that the number somewhat depends on the actual
dimensions of your movie. For example, if your movie is sized at
640x480, you can probably get away with using more slides than you
can if your movie is 1024x768.
Sorry, there simply are no hard concrete rules here. Just
guidelines and gut feeling.
Cheers... Rick