I want to record 6 hours of CD quality sound but Audition Crashes.

Okay, the real clue there is that you are recording in Waveform view. This doesn't record direct to file at all, and is entirely limited by the available space on your temporary drive. If you want to make a really long recording, then do it in Multitrack view, where the file will be written direct to disk, and not have the rather severe limitation of being a temp file first. And if your system crashes, recovery of everything up to that point is possible quite easily.

Okay, I'm not a Mac user but I still don't understand what Acrobat has to do with this at all. But with most computing systems, an item not being displayed means only that. It will still be using resources and running in the background. The only thing it won't be doing is using up screen real-estate.

The other thing is that if you save to an MP3, that's not what you will be editing, because Audition doesn't use them. What it does is decode your MP3 back to being a wav file, that it can edit. So for a six-hour file, I'm not in the slightest bit surprised that it takes ages to open! And when it's finished and you resave it, it has to be re-encoded. So you've inevitably lost quality, because it's a compressed format. It may be larger, but save it as a wav file, edit it as a wav file and then save the final result as an MP3. That's what the format was designed to be - a distribution format, not an editing one.