I tend to use individual sub-folders for each character, just for organisation's sake. The last movie I made had 507 seperate voice files in 19 folders, totalling about 240mb. Can't say what the "all files in one movie" limit is, as I always work scene by scene and assemble the finished product in an editing program, rather than struggling to get the whole thing out in one go (which is just asking for trouble if the movie is longer than 10 mins).
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