Rendering audio tracks to WAV files takes a long time

I'm rendering out separate 5.1 audio to WAV files (separate L, R, C, LFE, Ls, Rs files). This is a 10 minute short film and it taking 1 minute 15 seconds per track, and it has to do each one individually. I don't understand why it's taking so long. I can output the same audio tracks for a feature in about 5 minutes. This is a 10 minute short and it takes about 8 minutes. Why?
Also, there's no way to render the audio files without text being automatically added to the beginning of the custom filename I selected. For example, I'm getting "A6-0001_" at the beginning. Why can't we tell it not to add text to the beginning of the filename?
Also, there's no way to render the audio files without text being automatically added to the beginning of the custom filename I selected. For example, I'm getting "A6-0001_" at the beginning. Why can't we tell it not to add text to the beginning of the filename?