This is stupid, like microsoft level stupid. Every professional wants to dictate and then email the dictation to a processor or assistant. The paltry time limit on how much you can email means the user has to split it up. I just tried using "trim" and, like you, lost a significant amount of work. There is no "split" or "divide" button. Apple should fire the programmer who designed this.
Um, there's actually a legitimate reason for the time limit. Mail will crash if attachments are too big. Just try e-mailing your entire photo library to yourself in a single e-mail. It doesn't work. As for the Trim feature, give Apple your (constructive) feedback at http://www.apple.com/feedback/